About 14 bundles if 400 square feet is the roof surface, at three bundles per square with 10% waste. If it is the footprint of the house and the roof is a 6/12 pitch, the roof is 447 square feet and it takes about 15 bundles.
How many bundles of shingles you need for 400 square feet depends entirely on whether that figure is the roof surface or the floor area of the house, and most people mean the house. If 400 square feet is the roof itself, it takes about 14 bundles at three per square with 10% waste. If it is the footprint and the roof is a standard 6/12 pitch, the roof surface is larger — about 447 square feet — and it takes about 15 bundles. The tables below give both, at every common pitch.
This is what decides the answer, and most people mean the house. A roof is always larger than the footprint under it, because it is sloped — by 5% at 3/12 and by 41% at 12/12. Ordering against the footprint is the single most common reason a shingle order comes up short.
| If 400 sq ft is… | Roof area | Squares +10% | Bundles at 3/square |
|---|---|---|---|
| The roof surface itself | 400 sq ft | 4.4 | 14 |
| The footprint, roof at 3/12 | 412 sq ft | 4.5 | 14 |
| The footprint, roof at 4/12 | 422 sq ft | 4.6 | 14 |
| The footprint, roof at 6/12 | 447 sq ft | 4.9 | 15 |
| The footprint, roof at 8/12 | 481 sq ft | 5.3 | 16 |
| The footprint, roof at 10/12 | 521 sq ft | 5.7 | 18 |
| The footprint, roof at 12/12 | 566 sq ft | 6.2 | 19 |
Three bundles per square, 10% waste for a simple gable. A hip roof runs 15% and a cut-up roof with several valleys up to 20%.
| Waste | Suits | Squares | Bundles |
|---|---|---|---|
| 10% | Simple gable, no valleys | 4.4 | 14 |
| 15% | Hip roof | 4.6 | 14 |
| 20% | Cut-up roof, several valleys | 4.8 | 15 |
About 14 bundles if 400 square feet is the roof surface, at three bundles per square with 10% waste. If it is the footprint of the house and the roof is a 6/12 pitch, the roof is about 447 square feet and it takes about 15 bundles.
4 squares before waste, since a roofing square is exactly 100 square feet of finished roof. With 10% waste added you would order against 4.4 squares.
Only if you are working from the footprint. Pitch does not change the bundles per square — it changes how many square feet of roof sit above a given footprint, which is 5% more at 3/12 and 41% more at 12/12.
Slightly. Unopened bundles usually go back for credit, but a second delivery for three bundles costs a trip charge and stops the crew for half a day — and on a stripped roof that is a weather risk as well as a cost.