What is a roofing square?

A roofing square is 100 square feet of roof surface. One square of 3-tab asphalt shingles requires 3 bundles. This is the industry-standard unit for estimating roofing materials.

How does roof pitch affect material quantity?

A steeper roof has more actual surface area than the horizontal footprint. A 6/12 pitch multiplier is 1.118; 8/12 is 1.202; 12/12 is 1.414. The calculator applies the correct multiplier automatically.

How many bundles of shingles are in a roofing square?

Most asphalt shingles come three bundles to a square (100 sq ft). Some heavier architectural shingles need four bundles per square. The calculator converts your roof area into squares and then bundles, and adds waste for hips, valleys and ridges.

How do I measure my roof from the ground?

Measure the building footprint length and width, then multiply by the pitch multiplier for your roof slope (about 1.12 for a 6/12 pitch) to get the actual sloped area. The calculator applies the multiplier for you once you enter the footprint and pitch.

How many squares is a typical house roof?

Many single-family homes have roofs of about 20–30 squares (2,000–3,000 sq ft of surface), but it varies widely with house size, pitch and overhangs. Enter your own footprint and pitch for a figure specific to your roof rather than a rough average.

How much should I add for waste on hips and valleys?

Plan about 10% waste for a simple gable roof and 15% or more for complex roofs with many hips, valleys and dormers, where extra cutting is unavoidable. The calculator lets you set this waste factor when estimating bundles.

Roofing Calculator — Estimate Shingles & Roofing

How to use Roofing Calculator

The roofing calculator estimates the number of shingles (squares), underlayment and ridge cap needed to reroof a home. Enter the roof footprint area and pitch, and the tool calculates actual roof area, number of bundles, waste factor for valleys and hips, and an estimated material cost.

Enter the house footprint length and width.
Enter the roof pitch (rise over run, e.g. 6/12 for a 6" rise per 12" run).
Add number of dormers, valleys and hips if applicable.
Set a waste factor (10–15%).
Review actual roof area in squares, bundle count and estimated materials.

Your data never leaves your device — 100% private processing.

Roof pitch, area and squares

One roofing square = 100 sq ft of roof surface. Actual roof area > footprint because of slope. Pitch multiplier for a 6/12 pitch ≈ 1.118; for 8/12 ≈ 1.202; for 12/12 ≈ 1.414. Actual area = footprint area × pitch multiplier. Standard three-tab shingles: 3 bundles per square. Architectural (dimensional) shingles: 3–4 bundles per square. Always add 10–15% for waste, hips, ridges and valleys.

Roof pitch multiplier reference
Pitch (rise/run)	Pitch multiplier	Slope category
2/12	1.014	Low pitch
4/12	1.054	Low-moderate
6/12	1.118	Moderate (most common)
8/12	1.202	Moderate-steep
12/12	1.414	Steep (45°)

Shingle types and lifespan

Three-tab asphalt shingles: 20–25 year lifespan, 60–80 mph wind rating, cheapest option. Architectural (dimensional) shingles: 30–50 year lifespan, 110–130 mph wind rating, most popular. Premium designer shingles: 50+ year lifespan, simulate slate or wood shake appearance. Metal roofing: 40–70 year lifespan, most durable but 2–4× the cost of asphalt. Choose based on local climate, wind and budget.

Worked examples

40×30 ft footprint, 6/12 pitch

Inputs: 1,200 sq ft × 1.118 ÷ 100 = 13.4 squares

Result: ≈ 40 bundles (3-tab); +10% waste ≈ 44

Same footprint, steeper 8/12 pitch

Inputs: 1,200 × 1.202 ÷ 100

Result: ≈ 14.4 squares (~43 bundles)

Underlayment for 13.4 squares

Inputs: synthetic roll ≈ 10 squares each

Result: ≈ 2 rolls plus ridge cap

Shingle type comparison (typical planning figures)

Shingle type comparison (typical planning figures)
Shingle type	Lifespan	Wind rating	Relative cost
3-tab asphalt	20–25 yr	60–80 mph	$ (lowest)
Architectural	30–50 yr	110–130 mph	$$
Designer / premium	50+ yr	130+ mph	$$$
Metal	40–70 yr	140+ mph	$$$$

Glossary

Roofing square: 100 square feet of roof surface — the standard roofing material unit.
Bundle: One-third of a roofing square of shingles; three bundles = one square.
Pitch: Roof slope expressed as rise over a 12-inch horizontal run (e.g. 6/12).
Valley: The V-shaped junction where two roof planes meet; requires extra flashing and shingles.

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Roofing Calculator

How to use Roofing Calculator

Roof pitch, area and squares

Shingle types and lifespan

Worked examples

Shingle type comparison (typical planning figures)

Glossary

Related reading

Frequently Asked Questions

Why use Roofing Calculator?

Common use cases

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