Roofing & Exterior calculator

Siding CalculatorSiding Square Footage and Cartons

Calculate siding square footage, siding squares and full packages from wall length, height, openings, package coverage and waste allowance.

Updated August 20, 2026

✓Instant estimateNo sign-up required

✓Clear formulaSee how the result is built

✓Editable inputsMatch your product

✓Practical roundingPlan real purchase units

⌑

Project details

Enter your measurements and material details.

Planning estimate only. Verify product specifications and project requirements before ordering.

💡Tip:

Gables add triangular wall area and should be calculated separately if average height does not capture them.

How the Siding Calculator works

The calculator multiplies total exterior wall length by average height, subtracts openings and adds waste. It also converts area to siding squares and full packages using the coverage value entered.

Formula

Net area = wall length × height − openings. Purchase area = net area × waste factor.

Measure before you buy

Add the lengths of exterior walls receiving the same siding. Use a representative wall height and calculate gables separately for better accuracy. Subtract large doors and windows, then enter actual package coverage.

Corners, starter strips, J-channel and trim are separate components.
Pattern alignment and short wall sections can increase waste.
Different siding profiles cover different square footage per carton.

Common questions

How many square feet are in a siding square?

A siding square represents 100 square feet of wall coverage.

Should I subtract windows and doors?

Yes for large openings, while a waste allowance can absorb small openings and cuts.

How do I calculate a gable?

Use triangle area: base × height ÷ 2, then add it to the wall area.

Does this include trim?

No. Corners, channels and trim pieces are separate.

Do I round packages up?

Yes. The calculator rounds to full packages based on the coverage you enter.

Worked example: Siding Calculator

Using the example inputs shown in the calculator — Total wall length (ft) = 120, Average wall height (ft) = 9, Windows and doors (sq ft) = 250, Coverage per package (sq ft) = 100, Waste allowance (%) = 10 — the result is 913 sq ft. This demonstrates the formula with a complete set of numbers rather than a hidden assumption.

The result breakdown also shows Siding squares: 9.13; Packages: 10. Replace the example values with field measurements and the exact product coverage, yield or package size you plan to buy.

For this siding calculator, the inputs with the greatest practical effect are total wall length, average wall height and windows and doors. Recalculate when any of those change; do not reuse a result from a different room, run, layer depth or product specification.