Deck Stair Calculator
A deck stair calculator lays out stairs from a deck down to grade. From the deck height (total rise), it finds the number of steps, the rise and run per step, and the stringer length. Deck stairs follow the same math as interior stairs but often land on a concrete pad. Enter your deck height below.
Enter your total rise (floor-to-floor height) to see the layout.
Estimate only. Confirm against your local building code: stairs, framing, rebar, roofing and retaining walls are structural and code-dependent. This site does not provide engineering judgment.
How Do You Calculate Deck Stairs?
To calculate deck stairs, measure the total rise from the top of the deck to the landing surface below, then divide by about 7.5 inches and round for the step count, as with any stairs. A 40 inch deck height gives 5 to 6 steps. The calculator returns the rise, run and stringer length, and you should plan a concrete pad or solid base where the stringers land, which the gravel and concrete calculators can size.
What Base Do Deck Stairs Need?
Deck stairs need a solid landing at the bottom, usually a concrete pad or a compacted gravel base, so the stringers do not sink or rot. The landing should extend at least 36 inches out from the bottom step. Size the pad with the concrete slab calculator or the base with the gravel calculator. A solid landing keeps the stairs stable and meets typical code requirements.
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Frequently asked questions
- How do I calculate deck stairs?
- Measure the deck height to the landing, divide by about 7.5 inches and round for the step count. A 40 inch deck gives 5 to 6 steps. The calculator gives rise, run and stringer.
- What do deck stairs land on?
- A concrete pad or compacted gravel base extending at least 36 inches from the bottom step, to keep the stringers stable and prevent rot.