# Roofing Calculator: Squares, Shingles & Materials

> Estimate roof area, roofing squares, shingle bundles, underlayment rolls, ridge cap and drip edge for a gable or hip roof from the building footprint and pitch.

**Quick answer:** A roof's true area is its footprint times a pitch factor: 1.118 at 6/12 and 1.414 at 12/12. One roofing square is 100 sq ft, about 3 bundles of shingles. A 28 × 40 ft house at 6/12 has about 12.5 squares, so roughly 42 bundles with 10% waste.

_Last updated: October 4, 2026. Estimates only; confirm quantities with your supplier._

## How to use a roofing calculator: roof area, squares and shingles

A pitched roof is bigger than the footprint of the building beneath it. The steeper the pitch, the more surface there is to cover. Multiply the footprint (including overhangs) by a **pitch factor** to get the true roof area.

```
pitch factor = √(1 + (rise ÷ 12)²)
roof area = footprint × pitch factor
squares = roof area × (1 + waste) ÷ 100
bundles = squares × 3
```

Roofers measure in **squares**: one square equals 100 square feet. Architectural asphalt shingles usually come three bundles to a square.

### Pitch multiplier chart

| Pitch | Multiplier | Angle |
| --- | --- | --- |
| 2/12 | 1.014 | 9.5° |
| 3/12 | 1.031 | 14.0° |
| 4/12 | 1.054 | 18.4° |
| 5/12 | 1.083 | 22.6° |
| 6/12 | 1.118 | 26.6° |
| 7/12 | 1.158 | 30.3° |
| 8/12 | 1.202 | 33.7° |
| 9/12 | 1.250 | 36.9° |
| 10/12 | 1.302 | 39.8° |
| 12/12 | 1.414 | 45.0° |

### How to find your roof pitch

Place a level 12 inches along a rafter in the attic and measure straight up to the rafter. That vertical distance in inches is the rise (6 inches = 6/12 pitch). From the ground, you can also hold a level against the roof edge or use a phone inclinometer app.

### How much waste should you allow?

| Roof type | Waste |
| --- | --- |
| Simple gable | 10% |
| Hip roof | 12% |
| Valleys, dormers, chimneys | 15% or more |

### What else does a roof need?

Besides shingles you'll need underlayment, starter strips along the eaves, ridge cap shingles, drip edge, flashing, roofing nails, vent boots and, in cold climates, ice-and-water shield along the eaves and valleys. Steep roofs (8/12 and up) are dangerous to walk, so many homeowners hire a pro; use this estimate to check contractor quotes.

Walls under the roof? See the [siding](../siding-calculator/) and [insulation](../insulation-calculator/) calculators.

### Squares and bundles by roof size

For a 6/12 gable roof (pitch multiplier 1.118) with 10% waste and 3 bundles per square. Footprint includes the overhang.

| Footprint | Roof area | Squares with waste | Bundles |
| --- | --- | --- | --- |
| 1,000 sq ft | 1,118 sq ft | 12.3 | 37 |
| 1,500 sq ft | 1,677 sq ft | 18.4 | 56 |
| 2,000 sq ft | 2,236 sq ft | 24.6 | 74 |
| 2,500 sq ft | 2,795 sq ft | 30.7 | 93 |
| 3,000 sq ft | 3,354 sq ft | 36.9 | 111 |

### Roof pitch in degrees

| Pitch | Angle | Multiplier |
| --- | --- | --- |
| 2/12 | 9.5° | 1.014 |
| 3/12 | 14.0° | 1.031 |
| 4/12 | 18.4° | 1.054 |
| 6/12 | 26.6° | 1.118 |
| 8/12 | 33.7° | 1.202 |
| 10/12 | 39.8° | 1.302 |
| 12/12 | 45.0° | 1.414 |

### Worked example: a 2,000 sq ft hip roof at 8/12

A hip roof with a 2,000 square foot footprint (overhang included) at 8/12 has a multiplier of 1.202, so the surface is 2,000 × 1.202 = 2,404 sq ft. Adding 12% waste for a hip roof gives 2,692 sq ft, or 26.9 squares. At three bundles per square that is **81 bundles**.

### Gable, hip and complex roofs

The calculator assumes 10% waste for a simple gable, 12% for a hip roof and 15% for a roof with valleys, dormers and chimneys. More cuts and more edges mean more offcuts. Treat these as planning figures and let your roofer confirm the quantity for your design.

### Measuring safely

- Measure the footprint from the ground or from plans, and add the eave overhang on every side.
- Measure each separate section of a complex roof, then add them together.
- Do not climb a steep or wet roof without proper fall protection; hire a roofer if in doubt.

### Ordering tips

- Shingles are sold in whole bundles, so always round up.
- Keep one or two extra bundles from the same lot for later repairs, because color can vary between production runs.
- Order starter strips, ridge cap, underlayment and drip edge together with the shingles; the calculator estimates each.
- Check the coverage printed on your shingle package. Not every product is three bundles per square.

## Frequently asked questions

### How many bundles of shingles are in a square?

Most architectural and 3-tab shingles come three bundles to a square (100 sq ft). Some premium or heavy shingles are four bundles per square.

### How many bundles of shingles do I need for a 2,000 sq ft roof?

A 2,000 sq ft roof is 20 squares, so about 60 bundles; with 10% waste, 66 bundles.

### How do I find my roof pitch?

Measure the rise over 12 inches of horizontal run with a level and tape. 6 inches of rise over 12 inches of run is a 6/12 pitch.

### How much waste should I add for roofing?

Add about 10% for a simple gable roof, 12% for hip roofs, and 15% or more for valleys, dormers or complex shapes.

### How many squares are in a roof?

Divide the total roof area in square feet by 100. A 28 × 40 ft footprint at 6/12 pitch is about 12.5 squares before overhangs and waste.

### How long does a roof take to shingle?

A typical house takes a crew 1–3 days; DIY can take a week or more depending on size and pitch.

### How much does roofing cost per square?

Asphalt shingle roofs are commonly quoted at several hundred dollars per square installed, varying widely by region, pitch and tear-off. Get local bids.

### Does this calculator work for a flat or metal roof?

The area result does. For a flat roof, pitch 2/12 gives a multiplier near 1.0; use the area to order membrane, rolled roofing or metal panels instead of shingles.

## Sources and further reading

- [Asphalt Roofing Residential Manual: design and application methods](https://www.asphaltroofing.org/wp-content/uploads/2017/06/ARMA-Residential-Manual-Final-2.14.14.pdf) — Asphalt Roofing Manufacturers Association (2014)
- [National Roofing Contractors Association](https://www.nrca.net/) — NRCA: roofing guidelines