Stair Calculator
Calculate riser height, tread depth, number of steps, total run, and stair angle from floor-to-floor height with 2R+T comfort checks.
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What is Stair Calculator?
A stair calculator converts the vertical distance between two floors into a buildable stair layout: how many steps you need, how high each riser should be, how deep each tread should run, how much horizontal space the staircase consumes, and the pitch angle of the finished stringer. This version evaluates every whole-step option inside your riser limits and validates each against the 2R + T comfort rule used by residential building codes worldwide.
Key Benefits
- Eliminates trial-and-error math when dividing a floor height into equal comfortable steps
- Flags steep or shallow layouts before you cut a single stringer
- Handles unit conversion between centimeters and inches automatically
- Runs entirely in the browser with no signup or data upload
Common Use Cases
- •DIY homeowners sizing a deck, loft, or interior staircase
- •Carpenters checking whether a planned rise/run fits local building-code limits
- •Architects and drafters comparing layout options against available floor space
- •Students and apprentices verifying stair-math homework with instant feedback
How to Use the Stair Calculator
- Measure the total rise: Measure vertically from the finished lower floor to the finished upper floor and enter the value. Include finish floor thickness for accurate results.
- Set riser limits: Enter the minimum and maximum riser height allowed by your local building code, for example 17-19 cm or 7-7.75 inches.
- Review the recommendation: The tool lists every whole number of steps that fits, with riser, tread, total run, angle, and a 2R + T comfort verdict, and highlights the best option near a 32-degree pitch.
- Copy or apply the layout: Use the scaled profile diagram for a visual check, then copy the full result or mark the row that best matches your available horizontal space.
Key Features
- Solves riser height and tread depth from floor-to-floor height with adjustable riser limits.
- Checks every candidate layout against the 2R + T comfort rule and a 26.5-37.5 degree pitch band.
- Recommends the best whole-step layout tuned near a comfortable 32-degree stair angle.
- Renders a scaled SVG side profile of the recommended staircase for quick visual checks.
- Lists all valid step counts in a comparison table with one-click copy of the full result.
- Supports metric cm and imperial inch input with automatic conversion when switching units.
Frequently Asked Questions
What is the 2R + T comfort rule?
It is a classic stair design rule stating that twice the riser height plus the tread depth should total about 60-64 cm (24-25 inches). This calculator targets 63 cm and marks any layout inside the 59-65 cm band as comfortable.
What riser height and angle does the calculator recommend?
It scans every whole number of steps within your min/max riser limits, then picks the layout closest to a 32-degree pitch — a comfortable middle ground between steep ladders and shallow ramps.
What is the difference between steps and risers?
The riser count equals the number of vertical climbs. The top surface usually lands flush with the upper floor, so total run is calculated as (steps - 1) treads, which is why the run uses one tread fewer than the riser count.
Should I use cm or inches?
Either. Switch units at any time and the inputs convert automatically. The comfort rule is checked in cm internally (63 cm target), matching common international building-code guidance.