MEASURE ONCE. PLAN EVERY STEP.
Stair calculator
with diagram.
Calculate stair rise and run, tread count, stringer pitch length and angle with a live diagram. Plan straight indoor or deck stairs in inches, feet, millimeters, centimeters or meters.
From floor to floor.
Down to the details.
Your stair dimensions and diagram.
View all dimensions & layout points
- First stringer rise cut
- Top tread support below upper floor
- Comfort comparison: 2 × rise + going
- Pitch-line vertical span
The first cut subtracts tread thickness, assuming finished landing levels and no additional packing. Stringer pitch length is the span of repeated rise/run modules, not the board length to order. Connections, end cuts, stringer depth, and bearing need separate allowances.
| Tread | Horizontal position | Finished height |
|---|
Positions are layout references, not saw-cut coordinates. Imperial fractions in exports are rounded to 1/16 in; use unrounded calculations to maintain equal risers.
N = ceiling(total rise / target riser). Equal rise R = total rise / N. Treads T = N − 1 (standard) or N (flush). Total run = T × going G. Angle = atan(R / G) in degrees. Stringer pitch span = T × √(R² + G²). Pitch span is not timber order length.
For straight flights, including indoor and deck stairs. Geometry estimates only; verify local requirements, headroom, supports, and connections before building.
START WITH THE RIGHT MEASUREMENTS
How to calculate stairs.
A good stair plan starts with finished floor levels.
Three steps take you from a measurement to a layout.
Measure the total rise
Measure vertically from the finished lower floor to the finished upper floor or deck. Include the final flooring on both levels. Floor-to-ceiling height is a different measurement.
Set the rise and run
Choose your units and a target riser height, or enter a fixed riser count. Set the tread going, or use an available total run to find the going that fits your space.
Check the whole flight
Read the equal riser height, tread count, footprint, and angle. Open construction details for thickness and top tread position. Check the reference notes, then print your plan.
THE MATH BEHIND THE MEASUREMENTS
Stair calculation formulas: rise, run and stringer length.
Risers count the vertical changes in height. Treads count the horizontal walking surfaces. With a standard top position, the upper floor completes the last rise, so there is one fewer tread.
Put your measurements to work ↗N = round up (total rise ÷ target rise)R = total rise ÷ N
Run = tread count × goingAngle = arctan (R ÷ going)
Length = tread count × √(R² + going²)Standard: tread count = N − 1. Flush: tread count = N. The stringer length above follows the tread pitch; the diagonal from lower floor to upper landing uses different endpoints.
CHECK IT WITH A REAL EXAMPLE
Stair calculation examples in feet and meters.
Both examples use the standard top tread position
and round the riser count up.
A 9-foot floor-to-floor rise
108 in total rise ÷ 7.5 in target = 14.4.
Round up to 15 risers at 7.2 in, with 14 treads.
- Tread going
- 10.5 in
- Total run
- 147 in / 12 ft 3 in
- Stair angle
- 34.4°
A 2.8-metre floor-to-floor rise
2,800 mm total rise ÷ 180 mm target = 15.56.
Round up to 16 risers at 175 mm, with 15 treads.
- Tread going
- 280 mm
- Total run
- 4,200 mm / 4.2 m
- Stair angle
- 32.0°
READ YOUR RESULTS
Stair calculator with diagram: what the drawing shows.
Follow the finished stair profile, then check the dimensions behind it.
A dimensioned side view
The live diagram labels total rise, total run, equal riser height, tread going, stair angle and stringer pitch length. The numbered horizontal surfaces are treads. In a standard flight, the upper floor completes the final rise, so 15 risers need 14 separate treads.
Open View all dimensions & layout points for each tread’s horizontal position and finished height. These cumulative measurements help you check the drawing against your measurements.
Printable stair plans and a formula PDF
Use Print / save PDF for the current straight-flight results and dimension table. Download diagram saves the drawing as an SVG image; Dimensions CSV saves the numbers for a spreadsheet. The printable results also include the calculation formulas.
A scaled screen drawing is not a full-size cutting template. Confirm the layout on the actual material. For more detail, see how to read a staircase diagram.
FROM DIMENSIONS TO LAYOUT
Stair stringer calculator: length, layout and first-step cuts.
A stringer supports the treads. Its repeated rise and going set the stair pitch.
How to calculate stair stringer length
First calculate the equal riser height, R, tread going, G, and tread count, T. This calculator reports the repeated pitch span: T × √(R² + G²). For 15 risers at 7.2 inches and 14 goings at 10.5 inches, the pitch span is about 178.24 inches.
The floor-to-floor diagonal uses different endpoints: √(total rise² + total run²). In that same example it is about 182.41 inches. Neither number alone determines the board you should order: end cuts, bearing, attachment and remaining stringer depth also matter.
Standard versus flush stringer mounting
With the standard top position, the uppermost tread is one riser below the upper floor. A flush top tread projects outward at upper-floor level and adds one going to the footprint. Select the matching arrangement in Construction details.
The first stringer rise cut is the finished riser height minus tread thickness. For a 7.2-inch rise and a 1-inch tread, that is 6.2 inches. This assumes the lower bearing surface and finish levels match the measured setup.
How to lay out and cut stair stringers
Transfer the calculated rise and going with a framing square and stair gauges. Check cumulative heights, mark the bottom tread-thickness adjustment and resolve the top connection before cutting. Check one stringer in position before using it to mark the others. Do not extend saw cuts beyond the notch corners; the remaining material is part of the support.
A nominal 2×12 or 2×10 designation does not establish a safe stringer size. Timber species, grade, notch depth, span and loading need a suitable construction detail. A stair jack or stair carriage may refer to a supporting member in a particular framing system; check the drawing’s terminology.
Compare pre-cut and custom stair stringers before choosing a fixed-rise product. Match its actual dimensions to the finished total rise; do not compensate for a mismatch with an uneven top or bottom step.
DECKS, PORCHES AND OUTDOOR STEPS
Deck stair calculator with a diagram.
Use the main calculator for a straight exterior flight, with the final deck and landing levels.
Measure the finished deck rise
Measure from the finished landing pad to the top of the decking. A measurement to a joist or to soil that will later be excavated gives the wrong finished rise. For garden or landscape steps, establish the finished levels and drainage first.
Calculate the deck steps
A 36-inch rise with a 7.5-inch target needs 5 risers at 7.2 inches. Standard mounting gives 4 treads. With a 10.5-inch going, the run is 42 inches and the pitch span is about 50.93 inches.
Resolve the outdoor details
Enter the actual tread thickness and nosing. Check board gaps and manufacturer span limits, then design the footings, stringer connections, weather exposure protection and guards. See the guide to reducing slips on stairs.
TWO FLIGHTS, ONE EQUAL RISER HEIGHT
Stair calculator with a landing and diagram.
Explore two straight flights separated by an intermediate landing. Both flights use the standard top-tread arrangement.
| Flight | Rise | Risers / treads | Run | Pitch span |
|---|
The drawing shows an inline arrangement. Pitch spans are not timber order lengths. This planner does not check building codes, headroom, landing structure, handrails or connections.
How to calculate stairs with a landing
Divide the full height by a whole number of risers, then split that count between the flights. Landing elevation equals the lower flight’s riser count × the equal riser height. Each standard flight has one fewer tread than risers, so the combined tread count is total risers − 2, plus the separate landing.
For the default 2.8 m example, 16 risers give 0.175 m each. An 8 + 8 split puts the landing at 1.4 m. Each flight runs 7 × 0.28 = 1.96 m; adding the 1 m landing gives a 4.92 m inline footprint. If the landing is already built, measure its actual elevation and calculate each flight from those fixed levels.
L-shaped, U-shaped and turning staircases
An L-shaped staircase turns 90° at a landing; a U-shaped staircase returns through 180°. You can use this planner’s individual flight dimensions to start a layout, but its combined straight length is not the footprint of a turning staircase. Draw each flight in plan with the stair width, landing dimensions and separation between flights.
Winder treads and spiral stairs need walking-line and turning geometry. Alternating-tread stairs and ship ladders also require a dedicated design. This tool does not calculate those arrangements or generate a 3D construction model. See the guide to stairs with a landing.
METRIC AND IMPERIAL
Calculate stairs in meters, centimeters, millimeters, feet or inches.
Metres and meters describe the same unit. Select the unit before entering a measurement.
For a metric stair calculator, select Metres (m), Centimetres (cm) or Millimetres (mm). Changing the selection converts the dimensions already entered. Use decimal points without unit suffixes or thousands separators: enter 2800 in mm mode, 280 in cm mode or 2.8 in m mode.
| Measurement | Meters | Centimeters | Millimeters |
|---|---|---|---|
| Floor-to-floor rise | 2.8 m | 280 cm | 2800 mm |
| Target riser | 0.18 m | 18 cm | 180 mm |
| Actual riser, 16 risers | 0.175 m | 17.5 cm | 175 mm |
| Tread going | 0.28 m | 28 cm | 280 mm |
| Standard flight run | 4.2 m | 420 cm | 4200 mm |
For imperial measurements, 1 foot = 12 inches and 1 inch = exactly 25.4 mm. Enter 9 feet 6 inches as 114 in inch mode or 9.5 in foot mode. Inch mode accepts fractions such as 7 1/2. Changing units does not select a different country’s building regulations.
CHOOSE THE COUNT, THEN CHECK THE FIT
Stair rise and run calculator: risers, treads and floor space.
“How many steps?” can mean risers or treads. Keep those counts separate.
Riser and tread calculation formula
For a target maximum rise, calculate N = ceiling(H ÷ target rise), then R = H ÷ N. In a standard straight flight, T = N − 1. Multiply T by the going to get the horizontal run. A 120-inch floor-to-floor rise with a 7.5-inch target gives 16 risers, 15 treads and a 157.5-inch run at a 10.5-inch going.
Calculate tread depth from available run
Select Available total run in the main calculator. With 15 risers, standard mounting and 140 inches of run, the going is 140 ÷ 14 = 10 inches. A result that fits the space may still be too steep or too shallow in tread depth for the applicable rules. Increasing the riser count reduces each rise but also adds a tread.
| Finished total rise | Risers | Each rise | Treads | Total run |
|---|---|---|---|---|
| 24 in / 2 ft | 4 | 6 in | 3 | 31.5 in |
| 36 in / 3 ft | 5 | 7.2 in | 4 | 42 in |
| 60 in / 5 ft | 8 | 7.5 in | 7 | 73.5 in |
| 96 in / 8 ft | 13 | 7.3846 in | 12 | 126 in |
| 108 in / 9 ft | 15 | 7.2 in | 14 | 147 in |
| 120 in / 10 ft | 16 | 7.5 in | 15 | 157.5 in |
These are arithmetic examples, not prescribed dimensions. An 8-, 9- or 10-foot ceiling height cannot determine stair length by itself. Measure finished floor to finished floor, including the floor assembly above the ceiling, and reserve separate space for landings.
PITCH, SLOPE AND COMFORT
Stair angle calculator and the 2R + G formula.
Angle measures steepness. The rise-to-going ratio determines it.
How to calculate stair pitch
Use angle = arctan(riser ÷ going), with the answer in degrees. For 7 inches of rise and 11 inches of going, the angle is 32.47°. Slope percentage is 100 × rise ÷ going, or 63.64% for that example. Percentage and degrees are different measurements.
Use a single equal riser and going when calculating the pitch. Dividing the full floor-to-floor rise by a standard flight’s total run mixes endpoints and produces a different angle.
The 7–11 rule and 2R + T
The 7–11 rule describes a 7-inch rise and an 11-inch going. The expression 2R + G adds two risers and one going; it gives 25 inches for that example. It is sometimes written 2R + T when T means tread going, not tread count.
Use this relationship to compare proportions alongside the actual code limits. It does not establish one ideal stair size for every building. The main calculator shows 2R + G in the expanded dimensions.
| Rise | Going | Angle | 2R + G |
|---|---|---|---|
| 6 in | 12 in | 26.57° | 24 in |
| 7 in | 11 in | 32.47° | 25 in |
| 7.5 in | 10 in | 36.87° | 25 in |
KNOW YOUR STAIRCASE
Stair dimensions: rise, going, nosing and stringers.
Use these definitions when measuring,
comparing results, or speaking to your builder.
Total rise & riser height
Total rise spans the two finished floors. Riser height is one vertical step. Divide the total rise evenly; do not leave a shorter last step to absorb a remainder.
Tread going & nosing
Going is the horizontal spacing between adjacent tread fronts. Nosing is the projecting lip. Adding nosing to every going would overstate your total run.
Tread thickness
The tread sits on the stringer. Subtract its thickness from the first stringer rise cut so the finished first step matches the remaining steps.
Stringer & stair angle
The stringer supports the treads. Stair pitch comes from one riser divided by one going. The pitch span helps plan the layout; it does not size the timber or its supports.
LOOK BEYOND RISE AND RUN
Plan the space around your stairs.
The flight must work with its landings,
floor opening, and edge protection.
Headroom & floor opening
Headroom is the vertical clearance above the sloping line through the tread nosings. Measure to the nearest ceiling, beam, or obstruction. Floor thickness and opening length matter; a staircase can fit its footprint and still have insufficient headroom.
To plan a stair opening, draw the upper floor assembly and the sloping nosing line in section. Check clearance at the opening edge and under every beam; ceiling height alone is insufficient. This page does not calculate the required opening length.
Stair width & landings
Check usable stair width at the relevant handrail height, plus the landing space at each end. Doors and changes in direction affect that space. For a landing between flights, measure and calculate each flight’s rise separately; do not divide the entire storey into one uninterrupted run.
Handrails & guards
A handrail provides a continuous grasping surface. A guard protects an open edge. They serve different functions, even when combined in one assembly. Their height, openings, returns, and attachment require checks beyond the rise-and-run calculation.
For a straight sloping rail segment, the geometric length between two chosen points is √(horizontal separation² + vertical separation²). Then account for the specified extensions, returns and fittings. Stringer pitch length is not a finished handrail order length; this page does not calculate baluster spacing.
Stringer support & connections
The geometry does not determine timber size, allowable span, number of stringers, or connector capacity. For timber decks, use the applicable details in the American Wood Council’s DCA 6 guide (2015 IRC basis) alongside local requirements, or obtain a project-specific design.
SUPPORT THE FULL TREAD WIDTH
How many stair stringers do you need?
The rise-and-run calculation cannot establish allowable stringer spacing.
First obtain the permitted spacing from the tread manufacturer and the applicable structural detail. If W is the distance between the centers of the two outer stringers, and S is the permitted maximum center-to-center spacing, an evenly spaced arrangement needs ceiling(W ÷ S) + 1 stringers. This is a spacing calculation, not a strength check.
For example, a 36-inch outer-stringer center span with a hypothetical 12-inch maximum needs 4 stringers. A 48-inch span needs 5; a 60-inch span needs 6. Actual stair width can include tread overhang beyond those centers. These examples do not recommend 12-inch spacing for every product.
The AWC DCA 6 wood deck guide, Figures 28–29 illustrates how stringer span, remaining notch depth and tread support work together within that guide’s scope. Composite decking, metal systems and different timber grades can require different details.
MEASURE THE SURFACE YOU ARE ESTIMATING
Stair area, runner length and material estimates.
These manual methods answer related estimating questions. The main tool calculates flight geometry.
Stair square footage versus footprint
For a straight flight, floor-plan footprint = total run × stair width. At 147 inches of run and 36 inches of width, that is 36.75 square feet, excluding landings. Divide square inches by 144 to obtain square feet.
For finish material, measure the actual tread surfaces and riser faces being covered and add their areas. The nosing profile, exposed faces, landings and waste can make this different from the plan footprint.
How to measure a stair runner
Follow the intended carpet path over each tread and down each riser with a flexible tape. Include the nosing contour, any landing, pattern repeat and the supplier’s fitting allowance. For a rough starting estimate, sum the tread depths and riser faces to be covered, then measure the actual path before ordering.
The sloping stringer length cuts diagonally across the steps; it is not the runner length. Runner width and installation method also affect the order.
Wood, steel, concrete and box steps
Equal rise and going describe a straight flight in any material. The structural design changes: steel needs connection and section design, concrete needs formwork and reinforcement design, and box steps use framed platforms rather than a notched stringer. This calculator does not produce those designs or calculate concrete volume.
Stair costs and a material list
Build a project estimate from tread and riser quantities, designed stringers or framing, landings, rails, fixings, footings, finishes and labor. Apply local supplier quotes and the specified waste allowance. Dimensions alone cannot give a reliable installed price.
For measuring and layout equipment, see tools for building stairs. Proprietary stair systems need their manufacturer’s own component schedule.
SMALL DETAILS. REAL DIFFERENCES.
Common stair calculation mistakes.
Check these before transferring
any dimensions to your material.
| The mistake | Why it changes the result | What to do instead |
|---|---|---|
| Measuring to unfinished floors | Floor finishes change the first or last finished rise. | Use the final walking-surface elevations at both ends. |
| Counting treads as risers | A standard flight uses the upper floor for its final rise. | Count vertical height changes. Standard treads = risers − 1. |
| Adding nosing to every going | It exaggerates the horizontal footprint. | Measure going from one tread front to the next. |
| Rounding each step independently | Small differences accumulate along the flight. | Keep the exact equal rise for layout, and check cumulative heights. |
| Ordering timber from pitch length alone | End cuts and connection details can require extra material. | Confirm the full stringer layout, bearing, and structural design. |
FROM THE FRAMING SQUARE TO YOUR SCREEN
A brief history of stair calculation.
The tools have changed.
The relationship between rise and run remains.
Geometry on the stringer
Traditional stair layout uses a framing square to transfer a chosen rise and run to the board. Stair gauges help repeat the position consistently. This method still connects the calculation to the physical work. See Johnson Level’s framing-square guide.
Less arithmetic by hand
Handheld construction calculators brought stair-specific functions into a portable tool. Johnson’s CALC-1500, for example, includes rise/run calculations, stair settings, and measurement conversion. Read the manufacturer’s manual.
A plan you can compare
Online stair calculators combine those calculations with editable inputs and drawings. This tool adds live unit conversion and a printable plan, making it easier to compare layouts. Measuring the actual site and checking the construction details are still part of the job.
DIMENSIONS ARE ONE PART OF THE PLAN
US residential stair dimensions: 2021 IRC reference.
The calculator compares selected dimensions with the 2021 IRC, Section R311.7. These are US residential reference values, not a worldwide standard or a building approval.
Your locally adopted edition and amendments govern. Metric selection changes units; it does not change the code reference.
*Headroom is not calculated here. Measure vertically from the sloping nosing line to the obstruction. Also verify stair width, landings, guards, handrails, nosing, and structural support. Exact unit conversions shown; code publications may round metric equivalents.
CHECK THE RULES FOR THE BUILDING
Standard stair rise and run: US, UK, Australia, Canada and New Zealand.
A measurement unit does not determine a building code. Location, use and the adopted edition matter.
The main calculator’s limited reference checks use the 2021 US IRC. Selecting metric units does not switch to Australian, British, Canadian or New Zealand requirements. The landing planner performs geometry only. A residential reference must not be applied automatically to commercial stairs, public access, portable classrooms or a required escape route.
| Location | Reference to consult | What to establish |
|---|---|---|
| United States | 2021 IRC R311.7 reference | Which residential or other code and amendments your authority has adopted. |
| United Kingdom | Approved Document K for England | The UK nation and stair-use category; England’s guidance is not a UK-wide approval. |
| Australia | NCC 2022 Housing Provisions, Part 11.2 | Applicable edition, building class and state or territory variations. |
| Canada, including Ontario | NRC Codes Canada publications | The province or territory’s adopted code, edition and stair category. |
| New Zealand | MBIE D1 Access Routes | The applicable stair category and compliance pathway. |
A FEW THINGS WORTH KNOWING
Stair calculator FAQs.
Practical answers before you start
marking out your stairs.
How many steps do I need for a 9-foot rise?+
For a 108-inch rise and a 7.5-inch target, the calculator rounds 14.4 up to 15 risers. Each finished riser is 7.2 inches. Standard mounting gives 14 treads; a flush top tread gives 15.
Can I calculate stairs in metres or centimetres?+
Yes. Select metres, centimetres, millimetres, feet, or inches. Changing units converts your existing measurements rather than reinterpreting the same numbers. For example, 2.8 m equals 280 cm or 2,800 mm. In inch mode you can enter decimals or fractions such as 7 1/2.
How do I calculate stair stringer length?+
For the repeated stair pitch, multiply the number of treads by √(riser height² + tread going²). A standard flight has one fewer tread than risers. This pitch length does not include the extra board needed for end cuts, bearing, connections, or stringer depth; verify the actual cut layout before ordering timber.
Can I use this as a deck stair calculator?+
Yes, for the geometry of a straight deck stair flight. Measure to the finished decking and finished lower landing, and enter the actual tread thickness. Decking gaps, footing design, timber sizing, stringer spacing, and connections require separate design checks.
What is the difference between standard and flush?+
Standard places the highest tread one full riser below the upper floor; the floor completes the climb. Flush adds a tread level with the upper floor, projecting outward. It adds one going to the footprint without adding another riser.
What is the 7–11 rule for stairs?+
It describes a 7-inch riser with an 11-inch going. The related comfort comparison, two rises plus one going, gives 25 inches for that combination. It is a starting point for comparison, not a universal rule or proof of compliance.
Why does my actual riser differ from the target?+
A staircase needs a whole number of equal risers. This calculator rounds the count up and divides the total rise by that count, keeping the finished rise at or below your target. Use fixed riser count to compare a different arrangement.
Does this work for spiral or turning stairs?+
The main calculator handles one straight flight. The landing planner divides the rise between two standard straight flights and shows their inline elevation. For L-shaped or U-shaped stairs, use each flight’s results with a separate plan of the turn and landing. Spiral stairs and winders need different geometry.