Stair Calculator (Risers & Treads)

How to use this calculator

Enter the total rise, your maximum riser height and the tread depth. The number of risers, actual riser height, total run and angle are calculated.

Formulas

risers = ⌈rise ÷ max riser⌉ riser = rise ÷ risers run = (risers − 1) × tread

Example

Floor-to-floor 2.7 m, max riser 180 mm, tread 270 mm:

• Risers = 15, each 180 mm
• Total run = 14 × 270 = 3.78 m
• Angle = 33.7°
• Check: 2R + G = 630 mm ✓

Always check your local building code for limits on riser, going, headroom and handrails.

Frequently asked questions

What is a comfortable riser height?

About 150–180 mm (6–7 in), with treads around 250–300 mm. Many codes cap risers at about 190–200 mm for homes.

Why is the number of treads one less than risers?

The top step is the upper floor itself, so there is one fewer tread than risers.

What is the 2R + G rule?

Twice the riser plus the going should be about 550–700 mm (often around 630 mm) for a comfortable stride.

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