Measure roof area by calculating length times width for each plane
To measure your roof for shingles, you need the total square footage of the surface you plan to cover. The most straightforward method is to measure the length and width of each roof plane (the flat sections), multiply them together, and add all the planes. A roof plane is any flat section between ridges or edges — a straightforward rectangular roof has two planes, while a more complex roof with valleys and dormers has many more.
You do not need to climb onto the roof itself. You can measure from the ground using the footprint of your house — the outline of walls and edges you can see from below — and then account for roof pitch (the angle or steepness). Pitch matters because a steep roof covers more area than a flat one, even if the house footprint is identical.
Key Takeaways
- Measure the length and width of each roof plane from the ground using your house footprint, then multiply to get square footage for that plane.
- Adjust your measurements for roof pitch using a pitch multiplier — a 6/12 pitch (common in many climates) uses a multiplier of 1.12, meaning you multiply your ground measurement by 1.12.
- Add 10 percent to your final total to account for waste, overlap, and cuts around edges, vents, and chimneys.
- Shingles are sold in bundles that cover roughly 33 square feet each, so divide your total by 33 and round up to find how many bundles you need.
- If your roof is very steep, has many valleys, or you are unsure of the pitch, a roofer can measure it in person or you can hire a measurement service.
Measure your house footprint and identify each roof plane
Start by sketching your roof as it looks from above. Walk around your house and note where the roof changes direction — where two sloped sections meet at a ridge, or where a section drops down to a valley. Each distinct flat section is one plane.
For each plane, measure the length and width from the ground. Use a tape measure along the base of the house wall (the length of that side) and measure from the edge of the house out to the edge of the roof overhang (the width, or how far the roof sticks out past the wall). Write these down for every plane. If your roof is symmetrical — both sides slope the same way — you only need to measure one side and use that number for both.
If you cannot measure directly on the ground because of landscaping or obstacles, you can measure the house itself using property records, a surveyor's report, or online mapping tools that show dimensions. Many county assessor websites list house dimensions, and Google Maps or similar tools let you measure distances on a satellite image.
Account for roof pitch using a multiplier
Roof pitch is written as a ratio like 4/12 or 6/12. The first number is the rise (how many inches the roof goes up) and the second is the run (how many inches it goes across). A 6/12 pitch means the roof rises 6 inches for every 12 inches it travels horizontally. Steeper roofs have higher first numbers.
To convert your ground measurement to actual roof area, multiply by a pitch multiplier. Common multipliers are:
| Roof Pitch | Multiplier |
|---|---|
| 4/12 | 1.06 |
| 5/12 | 1.09 |
| 6/12 | 1.12 |
| 7/12 | 1.16 |
| 8/12 | 1.20 |
| 10/12 | 1.30 |
| 12/12 | 1.41 |
To find your roof pitch, look at the roof from the side of your house. If you can see the slope clearly, you can estimate it by eye — a 6/12 pitch is fairly common and looks moderately steep. You can also measure it directly: place a level on the roof, measure up 12 inches along the level, then measure straight down to the roof surface. The distance down is your rise. Or ask a roofer or contractor who has seen your roof before.
Once you know the pitch, multiply each plane's length-times-width result by the multiplier. For example, a plane that measures 40 feet long by 20 feet wide is 800 square feet on the ground. With a 6/12 pitch, multiply 800 by 1.12 to get 896 square feet of actual roof area.
Add waste and overlap to your total
After you have calculated the area of all planes and adjusted for pitch, add 10 percent to the total. This accounts for shingles that overlap at edges, waste from cuts around vents and chimneys, and mistakes or damage during installation. If your roof has many valleys, dormers, or complex shapes, add 15 percent instead.
For example, if your total adjusted area is 2,000 square feet, add 200 square feet (10 percent) to get 2,200 square feet as your final number. This is what you use to calculate how many shingles to order.
Convert square footage to bundles of shingles
Shingles are sold in bundles. Most bundles cover approximately 33 square feet, though some cover 32 or 34 depending on the brand and shingle type. Check the bundle label or the product description to confirm coverage.
Divide your final square footage by 33. If you have 2,200 square feet, divide by 33 to get 66.7 bundles. Always round up — you cannot buy a partial bundle, so order 67 bundles. It is better to have a few shingles left over than to run short mid-project.
Measure roof pitch directly if you are unsure
If you cannot see the roof pitch clearly or do not feel confident estimating it, you can measure it yourself using a level and tape measure. Climb onto the roof (safely, with a harness or on a low-slope section) or measure from a ladder placed against the roof edge.
Place a 12-inch level on the roof surface, with one end pointing upslope. The level should be horizontal. Measure straight up from the other end of the level to the roof surface. That measurement is your rise. So if the distance is 6 inches, your pitch is 6/12.
Alternatively, many roofers offer free measurement services, and some will measure your roof from the ground using photos or binoculars. If you are hiring a contractor to install the shingles, they will measure the roof as part of their estimate, so you can use that number.
Account for complex roof shapes and features
If your roof has valleys (where two planes meet in a V-shape), dormers (small roof sections that stick out), or multiple levels, measure each section separately. Valleys and dormers require extra shingles because of the angles and overlaps, which is why adding 15 percent waste is important for complex roofs.
Vents, chimneys, and skylights do not need shingles, so you can subtract their area from your total if they are very large. A typical roof vent is about 1 square foot, and a chimney might be 10 to 20 square feet. For most residential roofs, these are small enough that subtracting them makes little difference, and it is safer to leave them in your calculation and have extra shingles.
Frequently Asked Questions
Do I need to measure my roof in person, or can I do it from the ground?
You can measure from the ground using your house footprint and roof pitch. You do not need to climb onto the roof. Measure the length and width of each wall section and the roof overhang, then adjust for pitch using a multiplier. This method is safe and accurate for most homes.
What if I do not know my roof pitch?
Look at the roof from the side of your house and estimate the steepness, or measure it directly using a level and tape measure. You can also ask a roofer, check your home inspection report, or contact your local building department — they may have records. If you are unsure, assume 6/12 (a common pitch) and add extra shingles to be safe.
How much extra should I order for waste?
Add 10 percent for a straightforward roof with few valleys or obstacles. Add 15 percent if your roof is complex, has many dormers or valleys, or if you are inexperienced with installation. It is better to have leftover shingles than to run short.
Can I use online tools or satellite images to measure my roof?
Yes. Google Maps, Bing Maps, and other tools let you measure distances on satellite images. You can also find house dimensions on your county assessor's website or property records. Combine this with your roof pitch to calculate area. This works well for straightforward roofs but may be less accurate for complex shapes.
What if my roof has a very steep pitch or unusual shape?
For steep roofs (10/12 pitch or higher) or roofs with many valleys and dormers, consider hiring a roofer to measure. Many offer free estimates and will measure the roof in person or using drone photos. This costs nothing if you hire them for installation and removes the risk of ordering too few shingles.