How many square feet is a roofing square?

A roofing square is 100 square feet of roof surface. A 2,400 square foot roof is 24 squares. Roofers quote material and labor per square, so the square count is the number every bid should agree on.

How many bundles of shingles are in a square?

Three. GAF's Timberline HDZ, which the manufacturer markets as America's number-one selling shingle, covers 33.3 square feet per bundle — three bundles to the 100 square foot square. Buy by the square and the bundles take care of themselves.

How do I calculate roof square footage from the ground?

Measure the footprint the roof covers, then multiply by the pitch multiplier. For a 6/12 pitch the multiplier is 1.118, so a 1,600 square foot footprint is about 1,789 square feet of roof. Skipping the multiplier under-orders material every time.

What is a 4/12 roof pitch in degrees?

18.43 degrees. Pitch is rise over run, so the angle is arctan(4 ÷ 12). A 6/12 is 26.57 degrees and a 12/12 is 45 degrees.

How much does a new roof cost per square?

HomeGuide publishes $200 to $500 per square installed for 3-tab asphalt, $400 to $600 for architectural shingles, and $500 to $1,600 for metal depending on the panel. Old roof removal adds $100 to $300 per square, per layer.

Does this calculator give me a quote?

No. It gives you the square count, the bundle count, and a published national price range applied to that square count. It cannot see your decking, your permit office, or what your roof is hiding, and none of those are small numbers.

Roofing calculator: squares, shingle bundles, and cost

A roofing square is 100 square feet of roof surface, and a standard shingle roof takes 3 bundles per square. Your roof is bigger than your house because it is sloped, so the number that turns one into the other — the pitch multiplier — is the whole job of the calculator below.

1. How big is the house underneath?

Measure the ground the roof covers, not the roof itself. Include the garage and any covered porch the roof runs over.

Length (feet)

Width (feet)

Footprint: 1,200 sq ft

2. What is the roof pitch?

Inches of rise for every 12 inches of run. If you have no idea, 6/12 is a common residential pitch — and the section below shows how to measure it.

6/12 is 26.6° and multiplies your footprint by 1.118. Walkable.

3. How cut up is it?

This is the waste factor — the extra material you buy to cut up.

Simple gable — two planes, no valleys (add 10%)Starter course and the cuts at the rakes. This is the low end of the published 10–15% rule of thumb.Hips, a valley or two, a few penetrations (add 15%)Every hip and valley is a diagonal cut, and the offcut is usually too small to reuse. The high end of the same published rule.Cut up — dormers, multiple valleys, skylights (add 20%, our figure)Our own step above the published rule, for roofs where almost every course gets cut twice. Nobody publishes a figure for this, so treat it as a starting point and let your roofer's own take-off overrule it.

4. What material?

Installed prices per square are HomeGuide’s published national ranges, not our measurements.

Multiple layers, a three-dimensional look, rated to about 130 mph. The usual step up from 3-tab.

5. How many layers are coming off?

Removal is priced separately at $100 to $300 per square, per layer. Pick zero if you are roofing over or building new.

Your roof

13.4 squares

1,342 sq ft of roof surface, from a 1,200 sq ft footprint at 6/12.

Footprint: 1,200 sq ft
× pitch multiplier (6/12): 1.118
Roof surface: 1,342 sq ft
Squares (÷ 100): 13.4
+ waste (15%), rounded up: 16 squares
Order: 48 bundles

Published price range

$6,709 to $12,075

Asphalt, architectural (dimensional), installed: $5,367–$8,050
Tear-off, 1 layer: $1,342–$4,025

Not a quote, and not our number. It is HomeGuide’s published national range applied to your square count. It does not include decking repair, permits, or anything your roof turns out to be hiding.

The link carries every number above, so you can send it to a roofer or paste it into a thread and it opens exactly like this.

Roof pitch calculator: x/12 to degrees, and back

Roofers say pitch as rise over run — “a 4/12” means the roof climbs 4 inches for every 12 inches it runs horizontally. Architects and solar installers usually want the same thing in degrees. Both come out of the same right triangle.

Pitch (rise per 12 inches of run)

/ 12

In degrees: 26.57°
As a percentage grade: 50.0%
Area multiplier: 1.1180

Angle in degrees

Type an angle to convert it back to the x/12 a roofer will recognize.

Roof pitch in degrees, percentage grade, and the multiplier that turns footprint into roof area
Pitch	Degrees	Grade	Area multiplier	Working on it
1/12	4.8°	8.3%	1.0035	Low slope — most shingles are not rated this flat
2/12	9.5°	16.7%	1.0138	Low slope — most shingles are not rated this flat
3/12	14.0°	25.0%	1.0308	Walkable
4/12	18.4°	33.3%	1.0541	Walkable
5/12	22.6°	41.7%	1.0833	Walkable
6/12	26.6°	50.0%	1.1180	Walkable
7/12	30.3°	58.3%	1.1577	Steep — roof jacks and harnesses
8/12	33.7°	66.7%	1.2019	Steep — roof jacks and harnesses
9/12	36.9°	75.0%	1.2500	Steep — roof jacks and harnesses
10/12	39.8°	83.3%	1.3017	Very steep — staging, and slower on every course
11/12	42.5°	91.7%	1.3566	Very steep — staging, and slower on every course
12/12	45.0°	100.0%	1.4142	Very steep — staging, and slower on every course

Every number in that table is trigonometry, not an estimate: degrees are arctan(rise ÷ 12), and the multiplier is √(rise² + 12²) ÷ 12. Check any row on a scientific calculator. 3 bundles make a square, because that is how much ground one bundle covers.

Prices last read from their sources on August 18, 2026. The geometry does not go stale; the prices do.

Roof square footage calculator: the math it runs

Every roof measurement starts on the ground. You measure the footprint the roof covers — the outline of the house, plus the garage and any porch the roof runs over — and then you account for the slope, because a sloped surface is always larger than the ground beneath it.

Pitch is written as rise over run: a 6/12 roof climbs 6 inches for every 12 inches it travels horizontally. Rise, run and rafter make a right triangle, so the rafter is √(rise² + 12²) long where the ground under it is only 12. Divide one by the other and you have the multiplier. For 6/12 that is 13.4164 ÷ 12 = 1.118. A 1,600 square foot footprint under a 6/12 roof is 1,789 square feet of roof.

That is the step that gets skipped, and skipping it under-orders material on every single job. It is also why a roof sq ft calculator that asks only for your house size cannot be right: it has no way to know the slope.

Roofing square calculator: what a square is

Roofing is not sold by the square foot. It is sold by the square, and one square is 100 square feet of roof surface. A 2,400 square foot roof is 24 squares. Materials, labor, tear-off and disposal are all quoted per square, which is why the square count is the one number every bid you collect should agree on. If one roofer says 28 squares and another says 34, somebody measured wrong or somebody is padding — and you should ask both of them to show the measurement.

Roof shingles calculator: bundles and waste

Shingles ship in bundles, and three bundles cover a square. That is not a rule of thumb but the manufacturer’s own spec: GAF lists 33.3 square feet per bundle for Timberline HDZ, which GAF markets as America’s number-one selling shingle — exactly three bundles to the 100 square foot square.

You never order exactly what you measured. Starter courses, hip and ridge cap, and every diagonal cut down a valley produce offcuts too small to use. Roofr, which makes estimating software for roofing contractors, puts the trade rule of thumb at “around 10% to 15% of the total material needed.” The calculator uses 10% for a simple gable and 15% once you have hips and valleys. The 20% option for genuinely cut-up roofs is ours, not anybody’s published figure, and it says so on the control.

Roof replacement cost calculator: the published ranges

We have not measured roofing prices. What we can do is show you somebody else’s measurement, name them, and apply it to your square count instead of to a made-up house. HomeGuide’s asphalt shingle cost guide publishes these installed ranges per square:

Asphalt, 3-tab — $200 to $500 per square installed. The flat, uniform shingle. Rated to about 60 mph wind, and the shortest-lived asphalt option.
Asphalt, architectural (dimensional) — $400 to $600 per square installed. Multiple layers, a three-dimensional look, rated to about 130 mph. The usual step up from 3-tab.
Asphalt, luxury / premium — $500 to $700 per square installed. Heavier designer shingles meant to imitate slate or shake.
Old roof removal — $100 to $300 per square, per layer, per HomeGuide’s roof replacement guide. Not charged if you are roofing over or building new.

For scale on the whole job: the same source puts the national average roof replacement at $10,800, with a usual range of $5,700 to $16,000. This Old House lands higher — $15,439 on average for a 2,000 square foot asphalt roof, with most projects between $6,885 and $23,993. We print both, because a homeowner shown only the lower number and then handed the higher bid has been misled by us, not by their roofer.

Metal roof cost calculator

Metal is a different price universe, not a step up from shingle, and the two common panel types are hundreds of dollars a square apart. HomeGuide’s metal roof guide publishes:

Metal, corrugated / exposed fastener — $500 to $1,200 per square installed. The cheapest metal roof and the easiest to install, but the exposed fasteners need re-tightening over the years.
Metal, standing seam — $900 to $1,600 per square installed. Concealed fasteners and overlapping panels, so there are no exposed screws to back out over the years. The priciest of the common metals.

Metal is also the one material where the bundle count on the calculator goes away: panels are cut to the length of the run, so the order is squares of panel, not bundles.

How to measure your own roof pitch

You do not need to get on the roof. From inside the attic, hold a level against the underside of a rafter, mark 12 inches along the level from where it touches, and measure straight up from that mark to the rafter. That vertical measurement in inches is your rise, and the pitch is that number over 12. A phone with an inclinometer app held flat against a rafter gives you the angle instead, and the converter above turns it back into an x/12.

Two roofs of identical square footage can be thousands of dollars apart in labor, and pitch is the biggest reason. Anything past about 7/12 stops being walkable, so the crew works off roof jacks and harnesses and every course takes longer.

What this calculator cannot see

It has no idea what your decking looks like under the old roof, and rotten sheathing is one of the common reasons a roofing bill grows after the contract is signed. It does not know your permit fees, your local disposal rates, how many valleys and skylights you have, or whether your metro just took a hail storm and doubled its labor demand. Use the square count to check whether three bids are describing the same roof. Use the price range to know whether a bid is in the neighborhood. Do not use either one to argue with a roofer who has been on your roof.

More on reading bids against each other: how much a roof replacement costs and how to tell if your quote is fair, and what to check before signing a roofing contract.

Once you know your square count, the next question is who does the work. We measure which roofing companies AI assistants actually recommend, metro by metro. Nobody can pay to be on these lists.

Not your city? See every metro we measure.

Questions people ask next

How many square feet is a roofing square?: A roofing square is 100 square feet of roof surface. A 2,400 square foot roof is 24 squares. Roofers quote material and labor per square, so the square count is the number every bid should agree on.
How many bundles of shingles are in a square?: Three. GAF's Timberline HDZ, which the manufacturer markets as America's number-one selling shingle, covers 33.3 square feet per bundle — three bundles to the 100 square foot square. Buy by the square and the bundles take care of themselves.
How do I calculate roof square footage from the ground?: Measure the footprint the roof covers, then multiply by the pitch multiplier. For a 6/12 pitch the multiplier is 1.118, so a 1,600 square foot footprint is about 1,789 square feet of roof. Skipping the multiplier under-orders material every time.
What is a 4/12 roof pitch in degrees?: 18.43 degrees. Pitch is rise over run, so the angle is arctan(4 ÷ 12). A 6/12 is 26.57 degrees and a 12/12 is 45 degrees.
How much does a new roof cost per square?: HomeGuide publishes $200 to $500 per square installed for 3-tab asphalt, $400 to $600 for architectural shingles, and $500 to $1,600 for metal depending on the panel. Old roof removal adds $100 to $300 per square, per layer.
Does this calculator give me a quote?: No. It gives you the square count, the bundle count, and a published national price range applied to that square count. It cannot see your decking, your permit office, or what your roof is hiding, and none of those are small numbers.

Built for homeowners by Most Recommended Roofers, which measures which roofers AI assistants actually recommend across U.S. metros. The geometry here is ours; the prices are HomeGuide’s and This Old House’s, named and linked above. How we measure.