Material Shopping List
- Field shingles— bundles
- Starter shingles—
- Ridge cap— bundles
- Underlayment—
- Shingles cost—
- Starter + ridge cost—
- Underlayment + tear-off—
- Estimated total—
Roof Pitch Multiplier Chart
| Pitch | Surface multiplier |
|---|---|
| Flat / low slope | 1.00 |
| 3:12 | 1.03 |
| 4:12 | 1.05 |
| 6:12 | 1.12 |
| 8:12 | 1.20 |
| 10:12 | 1.30 |
| 12:12 | 1.41 |
Multiply the flat footprint by this to get the actual roof surface area.
Shingle Waste Guide
| Roof | Waste factor |
|---|---|
| Simple gable / shed | 10% |
| Hip roof | 15% |
| Complex / cut-up roof | 20% |
More valleys, hips, and penetrations mean more cut-off waste.
Roof Type Examples
| Roof | Notes |
|---|---|
| Gable | Two slopes, low waste, easiest to estimate |
| Hip | Four slopes plus hips, more cuts and ridge cap |
| Shed | One single slope |
| Gambrel | Barn-style, two pitches per side |
| Complex | Multiple ridges, valleys, dormers, highest waste |
How Many Bundles of Shingles Do I Need?
Shingles are sold by the bundle, and most field shingles take three bundles to cover one roofing square, which is 100 square feet. So the chain is simple: find the actual roof surface area, divide by 100 to get squares, add a waste factor, then multiply by the bundles per square for your shingle. This calculator does that and then builds the rest of the shopping list, including starter shingles, ridge cap, underlayment, and a cost estimate, so you walk into the supply house with a real order instead of one lonely square-foot number.
Squares vs Bundles
A square is a unit of roof area equal to 100 square feet; it is how roofers talk about size and how shingles are rated for coverage. A bundle is a physical package of shingles, and it usually takes three bundles to make one square with standard three-tab or architectural shingles. Heavier premium and designer shingles can take four or five bundles per square because each shingle is thicker and covers less. Always check the bundle wrapper, since the bundles-per-square figure is printed there and is what actually determines your order.
Why Pitch Changes the Area
The footprint of your house is the flat area you would measure on the ground, but shingles cover the sloped roof, which is larger. The steeper the roof, the bigger the difference. A pitch multiplier converts footprint to surface area: a 6:12 roof multiplies by about 1.12, an 8:12 by 1.20, and a 12:12 by 1.41. Skipping this step is the classic way to order too few shingles, because a 2,000 square foot footprint on a steep roof can be 2,800 square feet of actual surface to cover.
Frequently Asked Questions
How many bundles in a square? Three for most three-tab and architectural shingles; four to five for premium and designer lines.
How much waste should I add? About 10 percent for a simple gable, 15 percent for a hip roof, and up to 20 percent for a complex cut-up roof.
What is starter and ridge cap? Starter is a strip along the eaves that seals the first course; ridge cap covers the ridge and hips. Both are bought separately from field shingles.
Do I need new underlayment? On a tear-off, yes, the whole deck gets fresh underlayment, plus ice and water shield at the vulnerable areas.