Stair Calculator
Stair Calculator divide total rise evenly number of stair risers tread run worksheetDivide a known rise evenly
Enter the finished-floor-to-finished-floor rise, your project-supplied maximum planned riser height, and planned tread depth. The worksheet rounds the riser count up, then divides the total rise equally.
This is an arithmetic worksheet, not a stair design
The calculator helps check equal division after you already have project dimensions and requirements. It does not select legal dimensions or approve a stair. Building rules vary by location, occupancy, stair type, landings, and existing conditions. Use approved plans and qualified local guidance.
Calculation method
Riser count is the total rise divided by the entered maximum planned height, rounded up. Actual equal riser height is total rise divided by that whole count. A simple straight flight normally has one fewer tread than risers because the upper floor serves as the final walking surface. Run is tread count multiplied by planned tread depth.
Worked example
For a 105-inch total rise and a 7.75-inch maximum planned riser, 105 ÷ 7.75 is about 13.55, so the worksheet uses 14 risers. Each equal riser is 7.5 inches. With 13 treads at 10 inches each, the arithmetic run is 130 inches.
Measure finished surfaces consistently
Total rise should use the same finished reference at both ends. Flooring, underlayment, landings, and tread material can change individual heights if they are ignored. Small accumulated errors matter because risers should be uniform. Verify the final layout from a single reliable datum.
Run is only one space requirement
The reported run covers equal tread depths in one straight flight. It excludes landings, nosing projection, stringer ends, walls, trim, clearance, headroom, turns, winders, and approach space. A stair that fits this arithmetic can still fail structural, access, or safety requirements.
Safety and limitations
This tool does not check code, headroom, width, handrails, guards, stringer strength, load, tread thickness, nosing, landings, openings, fire rules, or accessibility. Do not use it as construction approval. Have a qualified person verify measurements, design, permits, and the built work.
Stair Calculator FAQ
Why round the number of risers up?
Rounding down would make each equal riser taller than the entered maximum plan value.
Why are there fewer treads than risers?
In a simple floor-to-floor flight, the upper floor commonly acts as the last walking surface.
Does the result meet my building code?
No. The values are arithmetic outputs based on your inputs, not a compliance determination.