Stair Calculator

Work out the number of steps, riser height, run and stringer length.

Total rise (floor to floor)

Target riser height

Tread depth

Number of risers (steps) 15

Riser height 7

Total run 147

Stringer length 180.65

Formula: risers = round(total rise ÷ target riser); riser = total rise ÷ risers

Step-by-step with your numbers:

1. Values used:

2. Total rise (floor to floor) = 105

3. Target riser height = 7

4. Tread depth = 10.5

6. Number of risers = Total rise (floor to floor) / Target riser height = 105 / 7 = 15steps

7. Riser height = 7

8. Total run = 147

9. Stringer length = 180.65

Did we solve your problem today?

Design a straight staircase: how many steps you need, the exact riser height, the horizontal run and the stringer (the diagonal board) length.

The math behind it

Number of risers = total rise ÷ target riser height, rounded to a whole number; the real riser height is total rise ÷ that count.

Treads = risers − 1. Total run = treads × tread depth. Stringer = √(rise² + run²).

Comfortable stairs follow the rule: 2 × riser + tread ≈ 25 in, with risers around 7 in.

105 in rise, 7 in target → 15 risers of 7.0 in, 14 treads × 10.5 = 147 in run, stringer = √(105² + 147²) = 180.7 in.

What is a safe riser height?

Building codes commonly cap risers at ~7.75 in and require treads of at least ~10 in.