Free calculator · no sign-up
Deck stairs calculator
Enter the deck height and the steps fall out of it: how many, the equal rise of each one, the treads and the stringers — drawn in 3D with the rest of the deck. Free, no sign-up, and nothing is priced until you add your own rates.
The rule in four lines
1. Measure the total rise
Top of the finished deck boards to the finished ground where the bottom step lands. Not the frame, and not the grass before you level it.
2. Divide by the maximum rise, round up
The maximum step height comes from your country's practice, so the number of steps changes between the US and the UK for the same deck.
3. Divide the height again by that number
Every step must be the same. Rounding the rise instead of the step count is what leaves a short step at the bottom, which is both a trip hazard and a fail.
4. Set the going and the stringers
The going is the depth of each tread; deeper treads make a longer, shallower flight that needs more room in the garden. Three stringers suit a normal width flight.
A worked example
A 16 ft x 12 ft deck standing 3 ft above the ground, with US practice selected.
- Deck height above ground
- 3 ft (915 mm)
- Steps
- 5
- Rise per step
- 7.2 in — equal, and inside the US limit
- Treads
- 5
- Stringers
- 3
Switch the country to the UK and the same deck becomes 6 steps of 6 in, because the allowed rise is lower. The designer flags it when a rise goes over the limit and tells you to add a step.
Common questions
How do I calculate the stairs for a deck?
Measure from the top of the deck boards down to the finished ground. Divide that height by the tallest step you are allowed, round up to a whole number of steps, then divide the height by that number again so every step is identical. The last division is the part most hand calculations skip, which is why the bottom step ends up short.
How many steps will I need?
A deck 3 ft (915 mm) above the ground comes out at 5 steps of 7.2 in in the US and 6 steps of 6 in under UK practice, because the two countries allow a different maximum rise. The calculator picks the country's limit for you.
How many stringers?
Three for a normal flight: one each side and one in the middle. Wide flights and heavy composite treads need more, so check the tread's span table.
Does it price the stairs?
Only with your own rates. There are no averages and no invented figures here — the page gives you the steps, the treads and the stringers to buy, and the cost appears when you enter what you pay.
Is this a structural design?
No. It is a take-off you can check. Stair rise, going, handrails and the landing still have to meet your local rules and, where it applies, building control.
The stairs are part of the deck
Draw the whole deck once and the steps, boards, joists, posts, footings, railing and fixings are calculated in the same list. The complete pack provides the order-ready PDF and CSV.
Open my deck in 3D, with the cut listFree, no account. Nothing is priced until you add your own rates. See a sample pack
Calculate my deck