Calculating handrail dimensions
Handrail length isn't just the diagonal distance. You need to allow extra length for the handrail to extend beyond the top and bottom risers, which is a key safety requirement in many codes. Measure from the centre of the top newel post to the centre of the bottom newel post along the stair line, then add the necessary extensions.
| Measurement Component | Requirement |
|---|---|
| Stair line diagonal | Primary length |
| Top extension | Typically 300mm |
| Bottom extension | Typically 300mm |
Know your numbers in 30 seconds
Enter your step count, tread depth and riser height — the stair runner calculator gives you the exact length to order, in metres and feet, with waste included.
Open the stair runner calculatorWhatever you decide, get the numbers first: the stair runner calculator doubles as a stair runner length calculator, adding nosing wrap, landings, winders, pattern repeat and waste so you order the right length the first time.
Still deciding on material, width or pattern? Our hub on stair runners compares weaves, widths, backings and fitting styles side by side, then hands the numbers straight to the calculator.
Frequently asked questions
How do I measure handrail length?
Measure the diagonal distance along the stair line, then add the necessary extensions for top and bottom safety.
Are extensions mandatory?
They are often mandatory in building codes to help users transition safely on and off the stairs.
How high should a handrail be?
Usually 900mm to 1000mm from the tread line.
Does the calculator account for extensions?
You can enter your total length, and the calculator helps determine the necessary rail section length.
Can I mount a handrail to the wall?
Yes, wall-mounted rails have different requirements for clearance.
Is diagonal length enough?
No, you must include enough length for post mounting and safety extensions.
Does the rail angle affect length?
The angle determines the diagonal length; the steeper the stairs, the longer the rail section.
What material is best for handrails?
Hardwoods or smooth-surfaced synthetics that offer a comfortable, reliable grip.
Know your numbers in 30 seconds
Enter your step count, tread depth and riser height — the stair runner calculator gives you the exact length to order, in metres and feet, with waste included.
Plan your stair safety with our stair runner calculatorEvery guide is written from hands-on measuring and fitting experience, checked against the calculator’s own maths, and re-reviewed whenever prices or methods change. Read our editorial standards.