22.3607 is the example result. Read it using the units and relationship stated below.
Roof Valley uses plan valley length, roof rise, roof run.
Turning measured dimensions into a material plan
For roof valley, the relationship is Result = [Plan valley length] × √(1 + ((([Roof rise]) ÷ ([Roof run])))^(2)). The amount depends on the supplied plan valley length, roof rise, 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.
What the model includes
Result = [Plan valley length] × √(1 + ((([Roof rise]) ÷ ([Roof run])))^(2)) Check the dimension convention and include openings only where the model has a corresponding input. A percentage allowance is a planning adjustment, not a layout simulation. Retain the source drawing or measurement sheet next to the result. Confirm the supplier unit before ordering. Area, volume, board feet and mass cannot be substituted without the thickness or density relationship. Structural suitability and fixing details are outside a quantity estimate.
Example with the supplied inputs
Plan valley length: 20; Roof rise: 6; Roof run: 12. Result: 22.3607. The values are illustrative.
Compare one changed input
Plan valley length changes from 20 to 22. The result becomes 24.5967. All other inputs remain fixed.
Calculation rule
Result = [Plan valley length] × √(1 + ((([Roof rise]) ÷ ([Roof run])))^(2))
Inputs and output
| Input | Example value | Entry convention |
|---|---|---|
| Plan valley length | 20 | Measure plan valley length in the displayed unit. Convert the source measurement before entry if it uses another system; a changed label does not perform a unit conversion. |
| Roof rise | 6 | Use the source quantity represented by roof rise. Keep the counted population fixed and avoid mixing a unit value with a period total. |
| Roof run | 12 | Use the source quantity represented by roof 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 Plan valley length, Roof rise, Roof 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 Plan valley length 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 Plan valley length from 20 to 22 while keeping every other value fixed. The result becomes 24.5967. 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