HomeMaterialBaseHomeMaterialBase

Roofing calculator

Roofers buy squares. One square covers 100 sq ft of roof surface. You usually start from building footprint, multiply by a pitch factor, then add waste for hips, ridges, and cuts. Enter footprint (or known surface), pitch/slope factor, waste, and read squares. Bundle math for asphalt shingles can move to the shingle page; $/square guesses belong on the cost page with a hard disclaimer.

sq ft
sq ft
Optional
in
in
12%
0510152025

+12% so you don't come up short

ORDER ESTIMATEROOFING
Squares to order15.0
Order area1502.64 sq ft
Roof surface1341.64 sq ft
Pitch factor1.118
Waste12%
How it calculates
surface = footprint × √(1+(rise÷run)²) or entered; order = surface × (1 + 12%); squares = order ÷ 100.

Estimate only — not a contractor bid. Confirm bag yields and local codes before you pour or order.

When to use

Re-roof material sanity check; comparing two pitch assumptions; planning underlayment rolls by area.

When not to

Insurance claim writing. Steep multi-dormer mansions as one rectangle. Metal panel linear-foot takeoffs — use surface squares carefully until a dedicated metal page is live.

Assumptions

1 square = 100 sq ft. Surface ≈ footprint × slope factor (from pitch/slope tools). Waste default 10–15% (simple gable); more for hips/valleys/cut-up roofs. Underlayment often 1:1 with surface before overlap rules on the roll label.

Worked examples

Example 1

Footprint 1,200 sq ft, 6/12 factor ≈ 1.12, waste 12%
→ surface ≈ 1,344 → order ≈ 1,505 → ~15.1 squares

Round the way your supplier sells (often whole squares).

Example 2

Known surface 2,000 sq ft, waste 15% (hip roof)
→ order 2,300 → 23 squares

Hips eat more than a clean gable — waste is not optional optimism.

How it calculates

Footprint × pitch factor (or surface), waste, then squares.

  1. Enter footprint or known surface area.
  2. Enter rise/run for the pitch factor (skipped if surface is set).
  3. Dial waste; read squares and order area.
surface sq ft = footprint × factor (or enter surface directly)
order sq ft = surface × (1 + waste%)
squares = order ÷ 100

Common traps

  1. Footprint is not the roof — forget the factor and you under-order.
  2. Layers / tear-off — weight and dump fees are not in this calculator.
  3. Starter, ridge, hip caps — extra linear products.
  4. High CPC SERP is full of lead-gen — we stay materials-only on purpose.

Next tool

Bundles for asphalt → shingle calculator.

Pitch/slope factor → roof pitch · roof slope.

Rough $ → roof cost calculator (estimate only).

FAQ

Roof surface sq ft ÷ 100 after waste.

Related

Estimate only — not a contractor bid or engineered takeoff. Confirm bag yields and local codes before you pour or order.