Stair Dimensions – Rise, Run & Angle

This tool applies the formula Riser = Total Rise ÷ n; Tread = 63 − 2 × Riser; Angle = arctan(Riser ÷ Tread) directly to the measurements you enter, so the result is an exact quantity rather than a rough guess. Because stair dimensions is priced and delivered per unit - cubic meters, square meters, bags or tonnes - a small measurement error multiplies across the entire order, which is why the calculation is worth doing properly. Worked example: 3.0 m rise, 16 risers → 18.75 cm riser, 25.5 cm tread (63 − 37.5), angle 36.3°, run 3.83 m. One note from practice: Check the diagonal opening: run + 1 m headroom triangle must fit inside the floor opening. Enter the total rise and available run length, check the totals, then round up to the nearest whole bag, sheet or roll before you place the order.

1. 1

   Measure the space

   Record the total rise and available run length at the widest and longest points.

2. 2

   Enter the values

   Type the measurements into the calculator and select your units.

3. 3

   Apply the formula

   The tool computes Riser = Total Rise ÷ n; Tread = 63 − 2 × Riser; Angle = arctan(Riser ÷ Tread) for your inputs instantly.

4. 4

   Add waste and order

   Review the total with a 5-10% margin and round up to whole units.

• Using nominal as actual sizes

• Spacing joists too wide

• No ground-contact treatment