Calculated result
14risers
Risers to plan
Formula
FRM-STAIR-001risers = round(total rise ÷ target riser); run = (risers − 1) × tread; stringer = √(rise² + run²)
7.5 in
Actual riser
13 treads
Treads
130 in
Total run
Lumber & framing calculator
Stair calculator
Preliminary riser count, tread run and stringer length from total rise and target step dimensions.
By Feroz Sheikh · Formula FRM-STAIR-001 v1.0.0 · Tested formula
Formula
FRM-STAIR-001v1.0.0Project inputs
Enter your measurements. Switching units converts the same project, including coverage and unit rates. Package yields keep the unit printed beside each field.
Refine measurements and rates at any time. Your current values are included in the material-list PDF.
Planning estimate, not engineering advice. Confirm site measurements and product specifications. Calculation limits.
This calculator returns riser count, tread run and stringer length from total rise and target step dimensions. Formula FRM-STAIR-001 v1.0.0. Planning geometry only. Carry the run into an estimate. It does not approve a code stair or a headroom layout.
- Measure the finished floor-to-floor rise, not the rough opening alone.
- Enter a target riser and tread, then review the resulting actual riser and 2R + T check.
- Verify headroom, nosing, stringer stock, guards and local requirements independently.
Size chart
Stair rise chart (7.5 in target riser, 10 in tread)
Planning geometry. Local code still owns riser, tread, headroom and guards.
| Total rise | Primary | Check |
|---|---|---|
| 96 in | 13 risers | 7.38 in |
| 105 in | 14 risers | 7.5 in |
| 108 in | 14 risers | 7.71 in |
| 120 in | 16 risers | 7.5 in |
Metric example — same rise, metric display. A 105 in floor-to-floor at a 7.5 in target riser returns 14 risers on the metric path. Not a code stair.
- IRC R311. Riser, tread, headroom and guards are local-code checks. This page is planning geometry. ICC IRC — means of egress / stairs
Add your project costs
Add rates if you are pricing a related project line. Pick a currency — badges, inputs, and totals follow.
This page is geometry, not a material takeoff. Leave rates at zero unless you are pricing a related line. Construclytic does not fetch supplier prices.
How this calculator works
A transparent stair calculator takeoff.
Feroz SheikhWritten by Feroz Sheikh · founder
This calculator converts a finished floor-to-floor rise into a whole number of risers, then reports actual riser height, tread count, total run and stringer length from the target going.
Stair geometry here is a planning count of risers, treads and stringer length. It is not a building-code stamp, not an ADA review, and not a shop drawing for a stair shop.
Worked example. Example: a 105 in total rise with a 7.5 in target riser produces 14 risers at 7.50 in. Thirteen 10 in treads make a 130 in run and a 13.93 ft stringer; 2R + T equals 25.00 in.
See the example inputs and calculated result
This separate example uses the calculator's starting values in imperial units. It stays unchanged when you edit the tool above. Example rates, yields and dimensions are assumptions, not recommendations for your project.
| Input | Example value |
|---|---|
| Total rise | 105 in |
| Target riser | 7.5 in |
| Target tread depth | 10 in |
Example result: Risers to plan — 14 risers.
risers = round(total rise ÷ target riser); run = (risers − 1) × tread; stringer = √(rise² + run²)
Use the labelled units above when reproducing this example. To work in metric, switch the calculator to Metric; applicable measurements are converted, while product-specific units remain labelled.
- 1. Measure the finished floor-to-floor rise, not the rough opening alone.
- 2. Enter a target riser and tread, then review the resulting actual riser and 2R + T check.
- 3. Verify headroom, nosing, stringer stock, guards and local requirements independently.
Field notes that change the number
- Total rise is finished floor to finished floor, including the floor finishes you will actually have.
- Headroom, nosing and guard height are code items. Confirm them locally.
- A triangular concrete stair volume is a different calculator from a wood stringer layout.
Common mistakes
- Using rough framing height as finished rise.
- Forcing an even riser count by hiding a ¼ in error in the last step — that is the step people feel.
- Treating this layout as a permit document.
Need the broader workflow? Read the lumber & framing planning guide.
How-to: Concrete stairs: separate step wedges, waist slab and landings · How to count deck boards
Questions
Questions about stair calculator
Does this meet building code?
No. Riser, tread, nosing, headroom and guard rules vary by jurisdiction. Use this as geometry planning only.
Why is 2R + T shown?
Carpenters often check 2 × riser + tread as a comfort range. It is a planning check, not an approval.
How many stair risers for a 105 inch floor-to-floor?
A 105 in total rise at a 7.5 in target riser returns 14 risers. Tread run and stringer length sit on the sheet. Not a code approval.
What is the formula ID?
This stair calculator publishes formula FRM-STAIR-001, version 1.0.0. The ID stays on the result and on the estimate line.