Free calculator
Roofing calculator
Enter the footprint of your roof and its pitch to estimate the sloped roof area, the number of roofing squares and the shingle bundles to order. Every assumption is shown and can be changed.
Roofing calculator
Calculated on lokalmatch.com
Your results
Shingle bundles
45
- Roofing squares1 square = 100 sq ft (9.29 m²), waste included
- 14.8
- Sloped roof area
- 1,342sq ft
- Area with waste
- 1,476sq ft
- Pitch factor
- 1.118
Starter strips and hip and ridge caps are sold separately, by linear length.
Estimates for planning only. Confirm quantities with your supplier or contractor before you order.
On this page
How to measure for the roofing calculator
- Measure the outside length and width of the house at ground level, then add the roof overhang on each side (measure it under the eaves).
- Split an L-shaped or complex house into rectangles and enter each one as a separate area. Add a garage or porch roof the same way.
- To find the pitch, hold a level horizontally against a rafter in the attic, or against the rake edge from a ladder. Measure 12 in (or 12 cm) along the level: the vertical distance up to the roof, in the same unit, is the rise per 12.
- If parts of the roof have different pitches, run the calculator once per section and add the results.
Assumptions behind the roofing calculator
Every default below appears in the calculator and can be changed.
- Roof area = footprint × pitch factor. The factor is the square root of (1 + (rise ÷ 12)²): the length of roof for each unit of horizontal run.
- A roofing square is 100 sq ft (9.29 m²) of roof surface, as IKO defines it.
- Default waste allowance: 10%, the low end of the 10 to 15% range IKO gives. Raise it for hips, valleys, dormers and skylights.
- Default: 3 bundles per square. IKO lists 3 bundles per square for its Cambridge and Dynasty shingles. Other products differ, so check the wrapper.
- The footprint you enter should include the overhangs. Starter strips, hip and ridge caps, underlayment and flashing are not included.
| Pitch | Angle | Factor |
|---|---|---|
| 0/12 | 0.0° | 1.000 |
| 1/12 | 4.8° | 1.003 |
| 2/12 | 9.5° | 1.014 |
| 3/12 | 14.0° | 1.031 |
| 4/12 | 18.4° | 1.054 |
| 5/12 | 22.6° | 1.083 |
| 6/12 | 26.6° | 1.118 |
| 7/12 | 30.3° | 1.158 |
| 8/12 | 33.7° | 1.202 |
| 9/12 | 36.9° | 1.250 |
| 10/12 | 39.8° | 1.302 |
| 11/12 | 42.5° | 1.357 |
| 12/12 | 45.0° | 1.414 |
| 14/12 | 49.4° | 1.537 |
| 16/12 | 53.1° | 1.667 |
| 18/12 | 56.3° | 1.803 |
Roofing calculator: tips before you buy
- Ask for each quote to list the number of squares, the shingle product and the waste allowance used, so you can compare quotes fairly.
- Starter strips and hip and ridge caps are separate products sold by linear length: measure the eaves, hips and ridges separately.
- Stay off the roof: measure from the ground and the attic, or ask a roofer to measure for you.
- Compare your result with the roofer’s measurement. A big difference is worth asking about.
Roofing calculator: frequently asked questions
How many bundles of shingles are in a square?
IKO explains that three bundles are typically needed to cover one square (100 sq ft); each bundle of its Cambridge and Dynasty shingles covers about 33.3 sq ft. Some products differ, such as IKO Armourshake at 20 sq ft per bundle, so check the wrapper and adjust the bundles-per-square field.
What is a roof pitch factor?
It converts the flat footprint of a roof into its real, sloped surface. A 6/12 roof has a factor of about 1.118, so 1,000 sq ft of footprint becomes about 1,118 sq ft of roof. The table on this page lists the factor for every pitch from 0/12 to 18/12.
How much waste should I add for shingles?
IKO gives about 10 to 15% as a general range. A simple gable roof sits at the low end; hips, valleys and dormers mean more cutting, so allow more.
Does it work for metal or flat roofs?
The roof area works for any material. Squares and bundles only apply to shingles; for metal panels or a membrane, use the area with waste and the coverage the manufacturer gives.
Sources for the roofing calculator
We checked these references on September 10, 2026. Product figures vary, so read the label or data sheet of the product you choose.
Last reviewed September 10, 2026
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