Free and simple, type your house size, pick how steep the roof is, and get how many bundles of shingles to buy. No sign-up, no email.
Step 1: Measure the house from the ground: length and width in feet (the roof's flat footprint).
Step 2: Pick the roof pitch, how steep it is. A normal house roof is 6/12. Steeper roof = more area = more shingles.
Step 3: Press Calculate. You get the roof area, the squares, and the bundles to buy with 10% extra.
Step A: Flat area = Length × Width. Example: 40 × 20 = 800 sq ft.
Step B: A sloped roof is bigger than its flat footprint. For a normal 6/12 pitch, multiply by 1.118: 800 × 1.118 = 894 sq ft of roof.
Step C: Roofers count in "squares": 1 square = 100 sq ft, so 894 sq ft = 8.94 squares. Standard shingles: 3 bundles per square. With 10% extra: 8.94 × 1.1 × 3 = 29.5, so buy 30 bundles.
| House Size | Roof Area | Bundles to Buy |
|---|---|---|
| 20 × 30 ft | 671 sq ft | 23 bundles |
| 20 × 40 ft | 894 sq ft | 30 bundles |
| 30 × 40 ft | 1,342 sq ft | 45 bundles |
| 30 × 50 ft | 1,677 sq ft | 56 bundles |
| 40 × 50 ft | 2,236 sq ft | 74 bundles |
This uses the house footprint. If your roof hangs over the walls a lot (long eaves), the real roof is a bit bigger, measure the roof itself if you can do it safely.
1. Using the house area as the roof area. A sloped roof is always bigger than the flat house size under it. The pitch multiplier in this calculator fixes that.
2. Forgetting the overhang. Roofs extend past the walls. A big overhang can add 5–10% more area.
3. Assuming every shingle needs 3 bundles per square. Most standard shingles do, but some heavy types need 4 or 5. Check the bundle in the shop.
4. Only 10% extra on a cut-up roof. Roofs with many hips and valleys waste more, 15% extra is safer there.
A 'square' is the roofer's word for 100 sq ft of roof. A 900 sq ft roof is 9 squares.
For standard shingles, 3 bundles cover one square (100 sq ft). Some heavy architectural shingles need more, the bundle itself says how much it covers.
Pitch is written like 6/12: the roof rises 6 inches for every 12 inches across. A roofing app on a phone can measure it, or check the home's building papers. When in doubt, 6/12 is the most common house pitch.
No. This counts shingle bundles only. Underlayment, ridge cap shingles, nails and flashing are separate items.
The roof area and squares are still correct. Only the bundles part is about shingles, so ignore that number for metal panels.