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Roofing resources

Roofing Waste Factor Calculator

Compare 10%, 12%, 15% and 20% waste scenarios against your net roof area.

TRY THE CALCULATOR

Start with your inputs.

Example values are editable. These inputs do not measure a property.

Compare all four allowances. The calculator does not select a recommended waste percentage.

THE RESULT, EXPLAINED

Clear inputs. Clear results.

Choose your units and calculate to see the result and its assumptions. Changing an input clears the previous result.

How is waste calculated?

Multiply net roofing squares by the allowance percentage to find the added squares. Add that allowance to the net area. For example, 20 squares with a 15% allowance becomes 23 squares.

Synthetic planning example: 20 net squares, accessories excluded
Allowance scenarioAdded squaresTotal squares
10%2.022.0
12%2.422.4
15%3.023.0
20%4.024.0

Which percentage is right?

These are scenarios, not project recommendations. Required material depends on layout, product coverage, installation details, usable offcuts and purchase rounding. Roof type and line lengths alone do not determine the answer.

Read the waste guide

Check the assumptions behind an allowance.

Material orders

From quantities to a reviewed sheet.

Convert your area

Find net squares before adding waste.

YOUR ROOF. YOUR NEXT STEP.

Start with a clearer picture.

Check your property