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Roofing calculator

Roof squares, shingle bundles, underlayment, drip edge, starter, ridge cap, nails and tear-off from your house footprint and roof pitch. Plus a typical installed price range.

By the LocalServiceHQ editorial team
Updated Oct 28, 2026
Formulas listed below
Measure the footprint, not the roofYou never need to climb up. Footprint × pitch factor gives the true roof area.
Photo by Zohair Mirza on Unsplash

The layers in a shingle roof

Shingles + ridge capNailed in a set pattern; ridge cap covers the peak and hips.
top layer
Starter stripSealant strip along the edges that stops wind from lifting the first course.
eaves + rakes
UnderlaymentSynthetic felt; ice & water shield at eaves, valleys and penetrations.
whole deck
Drip edgeMetal flashing that sends water into the gutter, not behind the fascia.
all edges
Roof deckOSB or plywood sheathing. Soft or rotted sheets get replaced after tear-off.
7/16–5/8 in

How to use the roofing calculator

1
Measure the footprint
Length and width of the house from outside walls. Add the overhang; we add it on all sides.
2
Find the pitch
Rise in inches over 12 in of run. A phone level app on a rafter or the rake board works.
3
Pick shape and material
Hip and complex roofs need more waste and more ridge cap. Material sets bundles and price.
4
Add tear-off
Each old layer adds labor and dumpster weight. Then print the list or compare it with quotes.

Roof pitch multipliers

Multiply the footprint area by the factor to get the real roof surface. Steeper roofs have more area over the same footprint.

Pitch
Angle
Factor
2,000 sq ft footprint
3/12
14.0°
1.031
20.6 squares
4/12
18.4°
1.054
21.1 squares
5/12
22.6°
1.083
21.7 squares
6/12
26.6°
1.118
22.4 squares
7/12
30.3°
1.158
23.2 squares
8/12
33.7°
1.202
24.0 squares
10/12
39.8°
1.302
26.0 squares
12/12
45.0°
1.414
28.3 squares

Factor = √(1 + (rise ÷ 12)²). Before waste.

Roofing materials compared

The cheapest roof up front isn't always the cheapest over 30 years.

Material
Installed / square
Lifespan
Wind rating
Weight / square
3-tab asphalt
$400–$550
15–20 yrs
60–70 mph
~200–240 lb
Architectural asphalt
$450–$700
25–30 yrs
110–130 mph
~250–350 lb
Designer / impact (Class 4)
$650–$1,100
30–50 yrs
110–130 mph
~350–450 lb
Standing seam metal
$900–$1,600
40–70 yrs
up to 140 mph
~100–150 lb

Typical US ranges for planning. Class 4 impact shingles can lower insurance premiums in hail states; ask your insurer.

Typical roof sizes by home

For a quick sanity check on a quote. Your own measurements are always better.

Home
Footprint
Squares at 6/12*
Bundles (arch.)*
1,200 sq ft ranch
1,300 sq ft
14.5
48
1,800 sq ft ranch
1,950 sq ft
21.8
72
2,400 sq ft 2-story
1,350 sq ft
15.1
50
3,000 sq ft ranch
3,200 sq ft
35.8
118

*Footprint includes overhangs and attached garage; gable roof, 10% waste on bundles.

Roofing mistakes and quote red flags

!
Quote by "house size"A fair quote is priced per square from measured roof area. Ask for the squares number in writing.
!
No line for deck repairAsk the price per sheet of decking replaced so the bill doesn't jump after tear-off.
!
Reusing old flashingStep and chimney flashing is often reused to save time. New flashing prevents the most common leaks.
!
Missing ventilation planPoor attic airflow cooks shingles from below and can void the warranty.
!
Storm chasersAfter hail, out-of-state crews knock doors. Check the license in your state guide and never sign an insurance assignment on the spot.
!
Mixed-brand systemManufacturer warranties often require their own starter, cap and underlayment. Ask which system is being installed.

Roofing calculator FAQ

How do I calculate roof squares?

One roofing square is 100 sq ft. Multiply the house footprint (including overhangs) by the pitch factor, then divide by 100. A 52 × 32 ft footprint on a 6/12 roof is 1,664 × 1.118 = 1,860 sq ft, or 18.6 squares.

Most 3-tab and architectural shingles come 3 bundles per square. Some heavier designer and impact-rated shingles come 4 or 5 per square. Check the wrapper.

The multiplier that turns flat footprint area into sloped roof area. It equals √(1 + (rise ÷ 12)²): 1.054 for 4/12, 1.118 for 6/12, 1.202 for 8/12, 1.414 for 12/12.

About 10% for a simple gable, 15% for a hip roof and 20% or more for roofs with valleys, dormers and many cuts. Starter and ridge cap are counted separately.

Asphalt shingle roofs typically run about $400–$700 per square installed in the US, more for steep or complex roofs and for tear-off. Metal is often $900–$1,600 per square.

Many codes allow two layers of asphalt shingles, but not three. A tear-off lets the roofer inspect and repair the deck, and most manufacturer warranties prefer it.

Codes in cold climates require it along the eaves, usually from the edge to 24 in inside the warm wall. It is also standard in valleys and around penetrations everywhere.

Most single-family asphalt roofs take 1–3 days. Steep pitches, multiple layers, deck repairs and weather can extend it.

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