How do I calculate roof squares from pitch?

Multiply the roof's plan area (footprint including overhangs) by the pitch factor, √(1 + (rise/12)²), and divide by 100. An 8/12 roof has a factor of 1.202, so a 2,450 SF footprint is 29.45 squares of surface.

What waste factor should a hip roof have?

Common estimating practice is about 10% for a simple gable, 15% for a hip and 20% for a cut-up roof with valleys and dormers. When there is a measurement report, use its waste table.

When do steep and high roof charges apply?

Xactimate® carries separate steep charges for 7/12–9/12, 10/12–12/12 and over 12/12 slopes, and a high-roof charge for two stories or more. Desk estimates that assume a walkable single-story roof leave them off.

Free tool · roofers and adjusters

Roof Squares Calculator

Surface squares from footprint and pitch, the right waste for the roof style, the linear items, the steep and high charges, and the carrier's shortfall.

Roof footprint (plan area incl. overhangs)SF

Pitch/12Stories

Roof style (sets waste)

EavesLFRakesLFRidge+hipLF

Carrier's squares (surface)SQCarrier's waste%

Pitch factor

1.202

√(1 + (8/12)²)

Roof surface

29.45 SQ

Shingles with 15% waste

33.86 SQ

Carrier short by

2.51 SQ

Carrier orders 31.35 SQ.

Steep / high charges

Steep + High

Additional charge for steep roof - 7/12 - 9/12 slope · Additional charge for high roof (2 stories or greater)

Quantities for the supplement

Roof quantities — 8/12 hip roof, 2 stories
Footprint 2,450 SF × pitch factor 1.202 = 29.45 SQ surface.
Shingles with 15% waste (hip): 33.86 SQ.
Carrier: 28.5 SQ at 10% waste = 31.35 SQ → short 2.51 SQ.
Drip edge (eaves + rakes): 186 LF.
Starter course (eaves): 186 LF.
Ridge / hip cap: 148 LF.
Additional charge for steep roof - 7/12 - 9/12 slope: 29.45 SQ.
Additional charge for high roof (2 stories or greater): 29.45 SQ.

Waste percentages are common conventions; use the waste table in the measurement report when there is one.

Where roof estimates come up short

Three places: a waste factor meant for a gable roof applied to a hip, linear items (starter, drip edge, ridge cap) left off because they are not in the field-shingle line, and steep and high charges missing because the desk estimate assumed a walkable single-story roof. Each is a few hundred dollars; together they are often thousands.

The math is the same everywhere, but the volume is not. Most roof claims come from hail in Dallas–Fort Worth, Denver, Oklahoma City, Atlanta and Minneapolis–St. Paul, and from wind on the hurricane coast from Houston to Tampa and Miami. On two-story homes with steep, cut-up roofs, a gable-roof waste factor and missing steep and high charges cost the most.

Put the quantities into the supplement builder, and check the storm date with the hail history lookup.

Questions

How do I calculate roof squares from pitch?: Multiply the roof's plan area (footprint including overhangs) by the pitch factor, √(1 + (rise/12)²), and divide by 100. An 8/12 roof has a factor of 1.202, so a 2,450 SF footprint is 29.45 squares of surface.
What waste factor should a hip roof have?: Common estimating practice is about 10% for a simple gable, 15% for a hip and 20% for a cut-up roof with valleys and dormers. When there is a measurement report, use its waste table.
When do steep and high roof charges apply?: Xactimate® carries separate steep charges for 7/12–9/12, 10/12–12/12 and over 12/12 slopes, and a high-roof charge for two stories or more. Desk estimates that assume a walkable single-story roof leave them off.

Need the roof estimate written?

Send the measurement report and photos. We write the full roof estimate in Xactimate®, free for the first one.

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