A Stair Length Calculator helps you estimate the total diagonal length of a staircase. Enter the number of steps, rise height per step, and run depth per step to calculate the overall stair length.
This calculation is useful for planning stair stringers, framing, handrails, finishes, and other staircase materials.
How to Use the Stair Length Calculator
Enter the following values:
- Number of steps
- Rise height of each step
- Run depth of each step
The calculator returns the total diagonal stair length.
Use the same unit for rise and run, such as inches, centimetres, feet, or metres.
How Stair Length Is Calculated
The total stair length is the diagonal distance from the bottom of the staircase to the top. It forms the hypotenuse of a right triangle.
- Total rise is the combined vertical height of all steps.
- Total run is the combined horizontal depth of all steps.
- Stair length is the diagonal distance created by the total rise and total run.
Calculate Total Rise
Multiply the number of steps by the rise height of one step.
Total Rise=Number of Steps×Rise per Step
Calculate Total Run
Multiply the number of steps by the run depth of one step.
Total Run=Number of Steps×Run per Step
Calculate Total Stair Length
Use the Pythagorean theorem to calculate the diagonal length.
Stair Length=Total Rise2+Total Run2
Example Stair Length Calculation
Suppose a staircase has:
- Number of steps: 20
- Rise height per step: 7 inches
- Run depth per step: 10 inches
Step 1: Calculate Total Rise
Total Rise=20×7=140 in
Step 2: Calculate Total Run
Total Run=20×10=200 in
Step 3: Calculate Total Stair Length
Stair Length=1402+2002
Stair Length=19600+40000
Stair Length=59600=244.13 in
The total diagonal stair length is approximately 244.13 inches.
Important Stair Planning Notes
- Use the same unit for rise height and run depth.
- The calculator estimates the diagonal length only.
- Confirm whether your stair design counts the top landing as the final tread.
- Add extra length for stringer cuts, nosing, landings, connections, and material waste.
- Follow local building requirements for riser height, tread depth, headroom, handrails, guards, and stair width.
- Consult a qualified professional for structural stair design.
Frequently Asked Questions
What does the Stair Length Calculator calculate?
It calculates the total diagonal distance from the bottom to the top of a staircase based on the number of steps, step rise, and step run.
Is stair length the same as total run?
No. Total run is the horizontal distance of the staircase. Stair length is the longer diagonal distance from the bottom to the top.
What is stair rise?
Stair rise is the vertical height of one step.
What is stair run?
Stair run is the horizontal depth of one step.
Does the calculator measure stringer length?
It provides a diagonal stair-length estimate that can help with stringer planning. Final stringer length may require extra allowance for cuts, landings, nosing, and connections.
Do the number of steps and number of treads always match?
Not always. In some stair layouts, the upper landing acts as the final tread. Confirm how your project counts risers and treads before ordering materials.
Can I use feet, inches, centimetres, or metres?
Yes. Use any unit, but make sure rise height and run depth are entered using the same unit.
Is this result suitable for final construction?
Use it as a planning estimate. Final stair construction should follow approved drawings, local requirements, and professional guidance.
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