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Deck Stair Calculator

Divide the total rise into equal risers and inspect the stair run before discussing the layout with your designer.

Your measurements

Editable example

Use the unit on each label. You can also type feet and inches with ft and in, or the marks on your tape measure.

Example: replace these measurements

Your stair layout

6 equal risers

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Height of each riser
7 in
Separate treads
5
Total horizontal run
50 in
First-to-last marking slope
61.0328 in

The sloping measurement is not a finished stringer cut length. Confirm local requirements and attachment details.

Run 50 inRise 42 in
Side view, including the rise to the deck. This is stair geometry, not a stringer cutting or attachment plan.

The calculation

  1. ceil(42 ÷ 7.75) = 6 risers
  2. 42 ÷ 6 = 7 in per riser
  3. 5 × 10 = 50 in horizontal run

Before ordering, use the deck measurement, board layout & design handoff guide to check the inputs and take the right questions to the supplier. Choose another calculator.

How to plan the quantity

Measure total rise between the finished deck and finished landing. Dividing by the chosen maximum and rounding up gives the number of equal risers.

The deck acts as the top tread, so the number of separate treads is one less than the riser count. Total horizontal run is tread count times tread run.

The sloping reference length connects the first and last step marks. It is not a stringer cut length: the upper attachment, bottom cut, nosing and actual board geometry still need a detailed plan.

Before you order

  • The editable starting limits reflect the cited AWC guide, not a statement of the code at your address. Confirm riser, tread, headroom, landing, handrail and guard requirements locally.
  • This does not size or approve a cut stringer. Keep finished tread thickness and the bottom/top connections in the drawing.