How many bundles in a square?
Most 3-tab and laminated shingles come three bundles to the square, so 10 squares take 30 bundles before waste. Some designer shingles take four or more, so check the wrapper and set the calculator to match. Need squares first? Use the roof square footage calculator.
What waste covers
Shingle waste covers cutting on the field shingles. A common range is 10 to 15%, and more on cut-up roofs. Underlayment has a separate allowance for laps. Starter and ridge cap come from measured lengths, with a separate accessory waste setting.
Starter, ridge cap, and drip edge
Starter runs along the eaves, and many manufacturers call for it on the rakes as well. Hip and ridge cap covers the hips and ridges. Drip edge goes on the eaves and rakes in 10-foot pieces lapped 2 inches. Coverage per bundle varies by product, so every default is editable.
Ice and water shield
Where code requires it, the ice barrier runs from the eave to 24 inches inside the exterior wall line, measured level, and manufacturers such as GAF measure from the inside of the wall. Up the slope that is farther. With a 12-inch overhang and a 6-inch wall on a 6/12 roof, it is about 47 inches, so one 36-inch course falls short. At 8/12 and steeper, it must also reach at least 36 inches up the slope. Valleys are lined whether or not the eaves need an ice barrier. The calculator uses a 36-inch strip of ice and water shield, and the code also allows other valley linings. Roll counts allow for an end lap on each roll; check the cuts and add accessory waste for short runs or penetrations.
Underlayment
One layer covers roofs at 4/12 and steeper. From 2/12 to under 4/12 the code calls for two layers, so those squares count twice. An approved self-adhered system may have different layer requirements.
Checking a carrier's estimate
Run the carrier's squares and lengths through the calculator and compare line by line. Short starter, ridge cap, and drip edge quantities are where gaps hide. The guide to supplementing a roof claim covers what to do with them.
FAQ
How many bundles of shingles for 1,000 square feet?
Thirty bundles for 10 squares, or 33 with 10% waste, at three bundles to the square.
Do you deduct the ice and water shield from the underlayment?
Practice varies, so it is a setting. Leave it off to order full underlayment.