Use this stair stringer calculator for first-pass stair layout math. Enter the total rise in inches, the ideal riser height, and the tread depth. The calculator rounds the riser count, divides total rise by that count to get actual riser height, subtracts one to get tread count, and multiplies treads by tread depth to get total run. This is layout math only. Check the final stair against the plan set, local code, landing conditions, nosing details, headroom, and the inspector before cutting stringers.
Stair Stringer Calculator: Risers, Treads, and Run
Estimate stair risers, riser height, tread count, and total run from total rise, ideal riser height, and tread depth.
Stair Stringer Calculator
Enter total rise, ideal riser height, and tread depth. The calculator returns risers, actual riser height, treads, and total run.
Risers14 risers
Riser height7.7 in
Treads13 treads
Total run130.0 in
Estimates for planning only. Check the result against your plans and a supplier quote before you order.
How to Use the Calculator
Measure total rise from the finished lower surface to the finished upper surface. Do not measure rough framing if finish floors, decking, tile, or landing build-up will change the final height. Enter that number in inches. Next, enter the ideal riser height. The default is 7.5 inches, which gives a comfortable planning target for many stair layouts. Enter tread depth last. The default is 10 inches. The calculator returns risers, actual riser height, tread count, and total run so you can test the layout before marking a stringer.
The Formula
The formula starts with risers = round(total rise / ideal riser height). Actual riser height = total rise / risers. Treads = risers - 1 because the upper floor or landing acts as the final step. Total run = treads x tread depth. With 108 inches of total rise and a 7.5 inch ideal riser, the rounded riser count is 14. Actual riser height becomes 7.7 inches. Treads equal 13, and a 10 inch tread depth creates a 130 inch total run.
Layout Notes
The calculator gives a clean starting layout, but the framing still has to fit the job. Finished floor height, landing thickness, hanger details, stringer stock, tread material, nosing, skirt boards, and decking thickness can move the cut line. The total rise must be a finished dimension. A small measurement miss gets repeated across every riser. I measure rise more than once, write down the finish assumptions, and run the calculator before I touch the framing square.
Worked Example
Say I measure 96 inches from the finished lower slab to the finished deck surface. I use the 7.5 inch ideal riser and 10 inch tread depth. The calculator rounds 96 / 7.5 to 13 risers. Actual riser height is 7.4 inches. Treads equal 12, so total run is 120 inches. If the landing space cannot accept 120 inches of run, I test a different tread depth or revise the stair plan instead of forcing a bad stringer layout into the opening.
Code and Field Check
Stair rules depend on the project, use, jurisdiction, and inspection path. This calculator does not approve a stair. Check maximum riser, minimum tread, variation limits, landings, handrails, guardrails, headroom, nosing, illumination, and egress requirements against the governing documents. Then check the field conditions. A stair that works on paper can fail when a door swing, landing edge, beam, slab slope, or finish thickness steals space.
Measurement Checklist
Measure total rise from the same finished points the stair will serve. For a deck, that means the finished walking surface at grade or landing up to the finished deck surface. For an interior stair, include flooring thickness on both ends. Check the rise at more than one point when slabs or landings slope. Write down the finished materials beside the measurement. If a tile layer, deck board, or floor patch changes later, rerun the calculator before final layout.
Run and Landing Notes
Total run tells you how much horizontal space the treads occupy before landing and framing details are added. It does not include a required landing depth, door clearance, nosing projection, or skirt layout. Use the run output to test the stair footprint early. If the available space is short, do not squeeze the stair by ignoring tread depth. Rework the layout, landing, or stair direction while the problem is still on paper. I also mark the planned tread material beside the run so finished nosing and thickness do not get forgotten. That note keeps layout math connected to the actual finish package.
Stair Layout Reference
| Reference | Planning value | Field note |
|---|---|---|
| Riser count | round(total rise / ideal riser) | Finds a whole number of risers |
| Actual riser | total rise / risers | Use this number for layout checks |
| Treads | risers - 1 | The upper landing is the final step |
| Total run | treads x tread depth | Horizontal run before nosing and landing details |
| Critical input | finished total rise | Finish surfaces control the stair math |
FAQ
How do I calculate stair risers? Divide total rise by the ideal riser height and round to a whole number. Then divide total rise by that riser count to get actual riser height.
Why are treads one less than risers? The upper floor or landing acts as the final step. A stair with 14 risers has 13 treads between the lower floor and upper landing.
What total rise should I enter? Enter finished floor-to-finished floor rise in inches. Include decking, flooring, tile, or landing build-up that affects final height.
Can I cut stringers from this result alone? No. Use the result as layout math, then check code, plan notes, finish thicknesses, landings, headroom, and field conditions before cutting.