RightQty

Decks & carpentry

Stair / stringer calculator

Turn total rise and project-specific limits into a riser count, actual rise, tread positions, total run, diagonal length, and stringer quantity.

Stair geometry

Calculate stairs and stringers

Measurement system
Overage

Covers spillage, uneven depth, settling, and minor measurement differences.

Optional material costEnter your supplier's USD price

Only the named material is priced; other shopping-list items, tax, delivery, hardware, and labor are excluded.

No signup. Your measurements stay in your browser.

Your material estimate

Stringers to plan for

5stringers

Includes 10% overage and purchase-unit rounding where applicable.

Risers
14 risers
Actual riser height
7.71 in
Tread positions
13 treads
Total stair run
10.83 ft
Minimum diagonal stringer length
14.08 ft

Example estimate: default sample values are shown. Update the measurements and select Calculate before using or copying this list.

Take this to your supplier

Shopping list

  • Stringer stock4 layout stringers plus 10% allowance.5 pieces
  • Tread positions / assemblies13 required positions plus 10% allowance; board count per tread is not inferred.15 tread positions
Calculation assumptions
  • Riser count is the smallest whole count that does not exceed the entered maximum riser height.
  • Tread count is one fewer than riser count because the upper landing is not counted as a separate tread.
  • Diagonal stringer length is geometric minimum before end cuts, bearing details, and stock-length selection.
  • Local stair code governs rise, run, nosing, width, landings, guards, handrails, headroom, and stringer design.

Stair geometry

How rise, run, and stringers are estimated

1

Riser count

Divide total rise by maximum riser height and round upward.

2

Actual rise and run

Divide rise evenly; use one fewer tread and multiply by tread depth.

3

Stringers

Calculate diagonal length and place stringers across stair width at maximum spacing.

Code boundary

Enter limits from the applicable code and design

The reported diagonal is geometric stair length, not a guaranteed stock-board cut length. End cuts, bearing, notches, defects, grade, and available stock must be checked against the approved design before buying or cutting.

RightQty does not choose legal rise, run, width, nosing, landing, guard, handrail, headroom, or stringer-cut requirements. Verify every dimension before cutting lumber.