How do I calculate roofing squares?

A roofing square is 100 square feet. Take your building's footprint area and multiply by the slope factor for your pitch (a 6:12 roof is about 1.118× the flat footprint) — that's your roof area. Divide by 100 for squares.

How many bundles of shingles do I need?

Most architectural and 3-tab shingles are packaged 3 bundles per square (33.3 sq ft per bundle). Take your squares, add waste (10% for a simple roof, 15% for a cut-up roof with hips, valleys or dormers per NRCA), then multiply by 3 and round up to a full bundle.

Does it work for a hip roof, not just a gable?

Yes. Switch to Hip and it calculates the hip lengths (for hip-and-ridge cap) and the full-perimeter eave (for drip edge and starter) instead of a gable's rakes.

SCOPE LOGIC

Free contractor tools

Free Roofing Calculator

Enter your footprint and pitch and get squares, shingle bundles, underlayment, ridge cap, starter, drip edge and nails — each with the formula behind it. No sign-up.

Runs on the same estimating engine ScopeLogic uses to price real jobs.

Roof takeoff

Your roof

Footprint length (ft)

Footprint width (ft)

Pitch (rise : 12)

Waste NRCA default 10%

NRCA: 10% for a simple roof, 15% for a cut-up roof with several hips, valleys or dormers. Enter what fits yours.

Underlayment

Nail pattern

Roof area

—squares

—

shingle bundles (3/square)

—

underlayment rolls

—

starter bundles (100 lf ea.)

—

ridge/hip cap bundles

—

drip edge sticks (10 ft ea.)

—

ice & water rolls, eaves (75 lf ea.)

How we got this

Source: square = 100 sf · slope factor = √(pitch²+144)/12 · hip/valley factor = √(pitch²+288)/12 · shingles 3 bundles/square (33.3 sf ea.) · waste 10% simple / 15% complex (NRCA) · nails 320/square @ 4-nail, 480 @ 6-nail (80 shingles/square).

Reroof? Carry a contingency for hidden deck rot found at tear-off — a common source of change orders.

Free calculators — no sign-up. Powered by ScopeLogic.

But shingles are never the whole roof

Field and cap are the easy part. Here's the rest of a real bid.

You've got squares, bundles and underlayment dialed in. But a roof is won or lost on the parts most calculators skip.

Field shingles & underlayment — done
Ridge, starter & drip edge — done
Valley, step & chimney flashing
Ridge vent & soffit intake
Tear-off & disposal, dry-in labour
Your markup & the client price

Your numbers, grown up

The same roof, turned into a bid you'd actually send.

In ScopeLogic those quantities flow straight into a full estimate — flashing, ventilation, labour and your markup — and come out as a clean proposal your client can approve and pay online.

Estimate — Full re-roof, gableExample

Line item	Qty	Unit	Your price
Architectural shinglesfrom calculator	39	bundles	$4,875
Synthetic underlaymentfrom calculator	2	rolls	$220
Ice & water shield, eaves	1	roll	$135
Valley & chimney flashing	48	lin ft	$310
Ridge vent	40	lin ft	$260
Tear-off, disposal & labour	3	days	$3,150
Client proposal total			$10,830

Your cost and markup stay private — the client only ever sees the price.

Want the whole takeoff & estimating platform — not just the calculator? Try ScopeLogic free for 7 days →

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