Carpentry calculators for stairs, stringers and roofs
Type the height between floors to see how many steps you need. A 10 ft rise takes 16 risers of 7 1/2" and 15 treads.
Calculators on this site
Stair calculator
Risers, treads, total run and angle from one height, with an IRC check and a scaled drawing.
Stair stringer calculator
Framing-square settings, a mark for every step, throat and how many 2x12s to buy.
Roof pitch
Pitch in x/12, degrees and percent from rise and run or from a measured angle.
Board feet
Board footage and price for rough and dressed lumber.
Rafters
Rafter length, plumb and seat cuts, birdsmouth for common pitches.
Deck framing
Joists, beams, decking boards and screws for a rectangular deck.
Why another stair and roof calculator
Most carpentry math is simple once the numbers are right, and most mistakes come from small things: a finish floor left out of the rise, a remainder dumped into the bottom step, a decimal read as a fraction. The calculators here are built around those traps.
- Fractions you can mark. Results come to the nearest 1/16", the smallest step on a tape measure, with millimeters alongside.
- Even steps. The rise is always split equally. For a 10 ft height that means 16 risers of 7 1/2", not fifteen full steps and a short one.
- Code sections named. Each check cites the IRC 2021 section it comes from, so you can read the rule yourself or show it to an inspector.
- Drawings from your numbers. The side view is scaled to your input, which makes a wrong entry obvious at a glance.
- Formulas in plain view. Every page shows how the result was reached. The methodology page lists sources and how each calculator was tested.
Before you cut
A calculator is only as good as the measurement fed into it. Measure the rise at the exact spot the stair will land, include every layer of flooring, and recheck once the framing is up. Local building departments adopt the model code with their own changes, and they have the final say on your project.