22.3607 is the example result. Read it using the units and relationship stated below.
Roof Rafter Length uses rise, run.
Turning measured dimensions into a material plan
For roof rafter length, the relationship is Result = √(([Rise])^(2) + ([Run])^(2)). The amount depends on the supplied rise, run, rather than a live market price or a value imported from another record. Material quantities begin with the actual surface, volume or part dimensions. A footprint and a sloped surface are different measurements. Pack sizes, offcuts and layout can increase the order above the geometric requirement.
Source and result record
For roof rafter length, retain Rise, Run together with the output. Record the date of the source values and the unit convention used in the form. That record separates a change in the underlying case from a change in how the information was entered. A saved result without its source values cannot show which assumption produced it.
Example with the supplied inputs
Rise: 10; Run: 20. Result: 22.3607. The values are illustrative.
Compare one changed input
Rise changes from 10 to 11. The result becomes 22.8254. All other inputs remain fixed.
Calculation rule
Result = √(([Rise])^(2) + ([Run])^(2))
Inputs and output
| Input | Example value | Entry convention |
|---|---|---|
| Rise | 10 | Use the source quantity represented by rise. Keep the counted population fixed and avoid mixing a unit value with a period total. |
| Run | 20 | Use the source quantity represented by run. Keep the counted population fixed and avoid mixing a unit value with a period total. |
Output: 22.3607 is the example result. Read it using the units and relationship stated below. Use the formula to distinguish a cash amount, count, percentage or ratio.
How to use the page
Collect the inputs
Gather Rise, Run. Use one period and the units shown in the form.
Run the calculation
Enter the values and select the action. The calculation rule above explains how the inputs produce the result.
Compare a scenario
Change Rise on its own, keeping the other inputs fixed. Read both results before changing another assumption.
Worked example
With the example inputs listed above, the result is 22.3607.
Change Rise from 10 to 11 while keeping every other value fixed. The result becomes 22.8254. This comparison isolates that input; it does not forecast how other variables will respond.
Check the stated formula, units and limits before using the result in a decision.
Keep the displayed formula, input units and model scope with the result. Corrections or questions can be sent through the request section on this page.
Content updated: October 11, 2026