Stair Calculator

Calculate number of steps, rise per step, tread depth, and stair angle.

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Total rise (in)

Total run (in)

Preferred rise per step (in)

Result

Enter values to calculate.

Summary

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Detail

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Calculate the number of steps, rise per step, tread depth, and overall stair angle for a given total rise and run.

How It Works

How Stair Calculator Works

The calculator divides your total rise (vertical height to climb) by your preferred rise per step, rounding to the nearest whole number, since you can't build a fractional step. It then divides the total rise evenly across that number of steps to get the actual, slightly adjusted rise per step.

Tread depth (the horizontal depth of each step) is the total run divided by the number of steps minus one, since the top step's "run" is the landing itself rather than an additional tread within the staircase's horizontal span.

The stair angle is calculated using the arctangent of rise over run, converted from radians to degrees — this reflects the overall slope of the staircase and is commonly checked against building code comfort ranges.

Worked Example

See It In Action

A staircase with 108 inches of total rise, 120 inches of total run, and a preferred rise of 7 inches per step works out to 15 steps at 7.2 inches of rise each, a tread depth of about 8.57 inches, and a stair angle of roughly 42 degrees.

Real-World Use Cases

Who Uses Stair Calculator and Why

Planning step count and rise for a new interior staircase before cutting stringers.
Checking whether a proposed deck stair design falls within a comfortable, typical residential rise range.
Working out tread depth needed for a given total run when replacing an existing staircase.

Common Mistakes

Mistakes to Avoid

Treating the entered "preferred rise" as the final rise per step — the calculator rounds the step count to a whole number first, then redistributes the total rise evenly, so the actual rise per step will typically differ slightly from what you entered.
Ignoring local building code minimums and maximums for rise and run — a mathematically valid stair from this calculator can still fail an inspection if it falls outside your jurisdiction's requirements.
Forgetting that total rise is the full floor-to-floor height, not just the visible flight — mismeasuring this throws off every step in the calculation.

Pro Tips

Tips for Best Results

If the calculated actual rise looks uncomfortably far from your 7-inch preferred target, try adjusting the preferred rise slightly and recalculating rather than accepting an oddly steep or shallow result.
Measure total rise with a level and tape rather than estimating floor-to-floor height, since even a half-inch error changes the evened-out per-step rise across the whole staircase.

Troubleshooting

Fixing Common Problems

The calculated rise per step looks different from the 7 inches I entered. — That's expected — the tool rounds your total rise divided by the preferred rise up to a whole number of steps, then redistributes the exact total rise evenly across that count, which nudges the per-step figure slightly.

My calculated stair angle seems too steep to be comfortable. — Try increasing the preferred rise value's corresponding run (a longer total run for the same rise reduces the angle), or check whether your local code has a maximum rise per step that would force a shallower design.

Glossary

Terms Explained

Rise: The vertical height of a single step, or the total vertical height a staircase climbs.

Run: The horizontal depth of a single step's tread, or the total horizontal distance a staircase covers.

Stringer: The diagonal structural board that supports the treads and risers of a staircase.

FAQ

Frequently Asked Questions

What's a comfortable rise and tread combination?

A common building guideline is the "7-11 rule" — roughly 7 inches of rise paired with 11 inches of tread — though exact requirements vary by local building code, and steeper stairs generally need a shorter tread with a taller rise, and vice versa.

Why does the number of steps get rounded instead of calculated exactly?

You can only build a whole number of steps, so the calculator rounds to the nearest whole step count based on your preferred rise, then recalculates the actual rise per step so all steps come out equal.

What if the calculated angle seems too steep?

Try increasing the total run (making the staircase longer and shallower) or reducing your preferred rise per step — both lower the overall angle, generally between 30-35 degrees for a comfortable residential stair.

Should I measure rise and run in inches or another unit?

This calculator expects inches for both total rise and run, matching how stair dimensions are typically specified on residential construction drawings in the US.