Stair Stringer Calculator
Cut a stringer wrong and every step in the flight is off, so the math has to be right before the saw comes out. Enter your total rise, the vertical distance from the bottom landing to the top, below. The calculator figures the number of risers, the exact riser height, tread count, total run, and the stringer length you need to cut, and flags whether your numbers land inside typical code limits.
How this is calculated
Divide your total rise by a target riser height (around 7 inches is comfortable) and round to the nearest whole number, that's your riser count. Divide total rise by that count to get the exact height of each riser. Treads always number one fewer than risers. Multiply tread count by your tread depth to get total run. The stringer length is the hypotenuse: the square root of total rise squared plus total run squared.
A worked example
A deck 44 inches above grade: 44 divided by 7 is about 6.3, so round to 6 risers, giving an exact riser height of 7.33 inches each. That's 5 treads; at 10.5 inches deep, the total run is 52.5 inches. The stringer length is the square root of 44 squared plus 52.5 squared, about 68.5 inches. The calculator returns all of it the moment you enter the rise.
Common questions
Start with total rise, divide by about 7 inches and round for the riser count, then divide total rise by that count for exact riser height. Treads are one fewer than risers. The calculator runs the whole sequence and gives you the stringer length to cut.
Common US residential limits are a maximum riser around 7.75 inches and a minimum tread depth near 10 inches, but local codes vary. The tool flags when your numbers fall outside the usual range so you can check before building.
Divide the total rise by a comfortable riser height near 7 inches and round. A 44-inch rise lands at 6 steps. Enter your exact rise above for the precise count.
Rise is the total vertical height the stairs climb; run is the total horizontal distance they cover. Each individual step has its own riser height and tread depth. The calculator gives you all four numbers.
Estimates for planning. Verify against your supplier's units and your local building codes before ordering or building. For anything structural, follow your engineer or local code.