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Construction & home

Rafter Length Calculator

Find an ideal straight rafter length from rise and horizontal run.

Editable waste and coverage assumptionsCheck supplier specifications

Project measurements

Runs on your device

MATERIAL ESTIMATE

Your result

Let’s calculate.

Use the Calculate button to see your result.

Review the method below for assumptions and conventions.

How to use this tool

  1. Enter vertical rise, horizontal run.
  2. Select Calculate to view the result.
  3. Check the method and assumptions below before using the result.

The method, explained

Length = √(rise² + run²).

A WORKED EXAMPLE

Using vertical rise = 3 m, horizontal run = 6 m, the result is 6.70820393 m. Change these example inputs to match your task; use the method above to check each step.

What to keep in mind

Excludes ridge thickness, seat cuts, overhang and connection design. A material-quantity estimate, not a structural design or building-code check. Confirm site measurements, supplier coverage and waste before ordering.

Common questions

Which inputs does this calculation need?

Find an ideal straight rafter length from rise and horizontal run. Enter vertical rise in m, horizontal run in m. The filled example is editable and is not a saved personal record.

How should I interpret the result?

Excludes ridge thickness, seat cuts, overhang and connection design. A material-quantity estimate, not a structural design or building-code check. Confirm site measurements, supplier coverage and waste before ordering.

Methodology maintained by ClarityKit. How these tools are built and checked.