Stair Calculator

How this is calculated

Number of steps = total rise ÷ target riser height, rounded to the nearest whole number. The actual riser height is then recalculated so every step is exactly equal.

Planning a staircase

Stair layout starts with the total vertical rise — the floor-to-floor height the stairs need to climb — and a target riser height that falls within a comfortable, code-compliant range.

Formula

Example: a 108-inch total rise with a 7.5-inch target riser gives 108 ÷ 7.5 ≈ 14.4, which rounds to 14 steps, and an actual riser height of 108 ÷ 14 = 7.71 inches.

Quick reference table

Common pitfalls

• Ignoring local building codes — maximum riser height and minimum tread depth vary by region and should always be checked before building.
• Uneven risers — always use the recalculated "actual riser" figure for every step, not the original target, to keep steps identical.
• Forgetting headroom — stair design also needs adequate vertical clearance above each step, which this calculator does not account for.

Tips

• A common comfort guideline is that (2 × riser) + tread depth should fall between about 24 and 25 inches.
• Always measure total rise directly (finished floor to finished floor), not from architectural drawings alone, since actual construction can vary slightly.

Frequently asked questions

How many steps do I need for a staircase? Divide the total vertical rise by your target riser height and round to the nearest whole number — this calculator does that automatically and then recalculates the exact riser height so every step is equal.

What is a typical riser height for a home staircase? Most residential building codes call for a riser height between about 7 and 7.75 inches (roughly 175–200 mm), though local codes vary and should be checked directly.

Why does the calculator adjust my target riser height? The number of steps must be a whole number, so the exact riser height is recalculated by dividing the total rise by that whole number — keeping every step identical, which is both safer and typically required by code.

What is stair "run"? Run is the total horizontal distance the staircase covers, calculated as tread depth multiplied by the number of steps minus one, since the top step is level with the upper floor.

Why does uneven riser height matter? Even small differences between riser heights are a leading cause of trips and falls on stairs, which is why building codes typically require risers to vary by no more than about 3/8 inch (about 10 mm) within a single flight.

How many stairs do I need for a 9 foot rise? A 108-inch rise at a typical 7.5-inch target riser needs about 14-15 steps — enter 108 as the total rise for the exact count and adjusted riser height.

What is the standard tread depth for stairs? Most codes call for a minimum tread depth of about 10 inches (≈250 mm), with 10-11 inches common in practice.

Does this stair calculator include a landing? No — it covers a single straight flight. For stairs with a landing, calculate each flight separately and add the landing depth to the total run by hand.

Worked examples

Example 1 — Basement stairs: 96-inch rise, 7.5-inch target riser → 13 steps, actual riser 7.38 inches.

Example 2 — Standard interior flight: 108-inch rise, 7.5-inch target riser → 14 steps, actual riser 7.71 inches, run ≈ 130 inches at a 10-inch tread depth.

Example 3 — Shallower riser preference: 108-inch rise with a 7-inch target instead → 15 or 16 steps depending on rounding, giving a gentler climb than Example 2.