How much roofing material do I need? From a satellite measurement to a list
Shingles, underlayment, starter, drip edge, ice & water, cap, valley metal and nails: one formula per line, then a gable house with a dormer turned into a material list.
You need true roof area times your waste factor for the field materials, and the edge lengths by type for everything else. Shingles and underlayment come off area; starter, drip edge, ice & water, cap and valley metal come off eaves, rakes, ridges, hips and valleys; nails follow the shingle count; pipe boots get counted.
Below: one formula per line, then a gable house with a dormer taken to a finished list.
The inputs a list needs
A list needs two things from the measurement. True area: plan area times the pitch factor, √(1 + (rise ÷ 12)²), facet by facet. And the edge lengths split by type. One perimeter number can't tell you how much is eave and how much is rake.
That split is what turns a trace into a list. From a satellite measurement to a material order walks through which edge feeds which line.
One formula per line
The coverages below are assumptions, the same ones we use across these guides. Swap in the numbers on your wrapper.
Shingles. Bundles = true area × (1 + waste) ÷ 100 × 3. Standard 3-tab and architectural shingles typically run 3 bundles a square.
Underlayment. Rolls = true area × (1 + waste) ÷ 1,000, for synthetic rolls that cover 1,000 sq ft net after laps.
Starter. Bundles = (eaves + any rakes you start) ÷ 105 lf a bundle.
Drip edge. Sticks = (eaves + rakes) ÷ 9.83, a 10 ft stick less a 2 in. lap.
Ice & water. Rolls = (eaves × courses + valleys) ÷ 66, for a 36 in. roll of about 66 lf. How many courses at the eave is your manufacturer's and local code's call.
Hip & ridge cap. Bundles = (hips + ridges) ÷ 25 lf a bundle.
Valley metal. Pieces = each valley ÷ 10 ft, rounded up per valley, then added. A 7 ft valley still takes a full piece.
Nails. Boxes = order squares × 66 shingles × nails per shingle ÷ 7,200 a box. That's 4 nails a shingle standard and 6 where the wrapper calls for high-wind nailing.
Pipe boots. No formula. Count them by size, on site or from your photos.
Waste goes on the field lines: shingles, underlayment and the nails that follow them. Linear lines start at straight footage and round up once.
Worked example: a gable house with a dormer
The house: a 44 × 30 ft gable traced at the drip edge, ridge running the 44 ft way, at 7/12 (pitch factor 1.158). On the front slope sits a gable dormer 8 ft wide at 9/12 (pitch factor 1.25). Its side eaves run 4 ft back before they meet the main roof, and its ridge runs back until it dies into the main slope.
The measurement reads:
- Plan area: 1,320 sq ft, of which 53 sq ft is dormer roof
- True area: 1,267 × 1.158 + 53 × 1.25 = 1,467 + 66 = 1,533 sq ft, or 15.3 squares
- Eaves: 96 lf (44 + 44 main, 4 + 4 dormer)
- Rakes: 79 lf (four main rakes at 15 × 1.158 = 17.4 ft, two dormer rakes at 5 ft)
- Ridges: 53 lf (44 main, 9 dormer). Hips: none
- Valleys: 14 lf (two dormer valleys at about 7 ft)
- Pipe boots: 3, counted on site
Waste. A plain gable at this pitch would sit in the 6–10% bracket. The dormer adds valleys and trapezoid cuts, so it nudges the roof into 10–14%. One small dormer earns the low end: 10%. Our waste factor guide by roof type has the brackets.
Order area. 1,533 × 1.10 = 1,686 sq ft, or 16.86 squares.
| Line | From the measurement | Math | Order |
|---|---|---|---|
| Shingles | 1,686 sq ft with waste | 16.86 × 3 = 50.6 | 51 bundles |
| Synthetic underlayment | 1,686 sq ft with waste | 1,686 ÷ 1,000 = 1.69 | 2 rolls |
| Starter | 96 eave + 79 rake = 175 lf | 175 ÷ 105 = 1.67 | 2 bundles |
| Drip edge | 175 lf eave + rake | 175 ÷ 9.83 = 17.8 | 18 sticks |
| Ice & water, one course | 96 eave + 14 valley = 110 lf | 110 ÷ 66 = 1.67 | 2 rolls |
| Hip & ridge cap | 53 lf ridge, no hips | 53 ÷ 25 = 2.12 | 3 bundles |
| Valley metal | Two valleys at about 7 ft | 1 piece each | 2 pieces |
| Coil nails, 4 a shingle | 17 squares (51 ÷ 3) | 17 × 264 = 4,488 | 1 box |
| Pipe boots | Counted | By size | 3 |
Three lines deserve a second look.
Starter. 2 bundles cover 210 lf against 175 lf. If you skip starter on the rakes, it's 96 ÷ 105 = 0.91, and 1 bundle leaves 9 ft of slack.
Ice & water. Where code calls for two courses at the eave: 96 × 2 + 14 = 206 lf ÷ 66 = 3.12, so 4 rolls.
Nails. At 6 a shingle the field takes 17 × 396 = 6,732. That leaves 468 nails in the box for starter and cap, so take a second box.
The dormer's cheek walls need step flashing; count it per wall, like the boots. How to build a roofing material order from a measurement covers those lines and what the yard needs for delivery.
Where RoofStruct fits
RoofStruct gives you free, unlimited self-serve measuring and PDF reports, no card. You trace on satellite imagery or your own drone or phone photo, label the edges, and the PDF on any plan lists the lengths by edge type: eaves, rakes, ridges, hips and valleys. That's the middle column of the table above.
On Pro, the Material Order Builder builds the list from that measurement at the waste % saved on it. Every line stays editable before it goes to your supplier.
Where you trip
- Tracing the main roof and skipping the dormer. On this house that drops 8 ft of eave, 10 ft of rake, 9 ft of ridge and both valleys, and leaves 13 sq ft of true area at the wrong pitch.
- Rakes off the plan. The main rakes are 15 ft from above and 17.4 ft on the roof. Four of them at plan length shorts you 9 ft of drip edge.
- One course of ice & water by habit. Check what the eave needs before you count rolls.
- Rounding every step. Carry the decimals and round once, in the unit the yard sells.
FAQ
How many bundles of shingles do I need for 1,000 sq ft of roof?
30 bundles before waste, if the 1,000 sq ft is true area: 10 squares × 3. At 10% waste it's 33. If the 1,000 sq ft is the footprint, multiply by the pitch factor first.
How do I work out how much underlayment I need?
Take true area with waste and divide by the roll's net coverage. At 1,000 sq ft net a roll, the example roof's 1,686 sq ft takes 2 rolls.
Do I count the rakes for starter strip?
Only if you start the rakes. Many crews run starter on eaves only and let the shingle overhang the rake, so add rake footage when your manufacturer or your own practice calls for it.
How many nails do I need per square of shingles?
At 66 shingles a square, 264 nails at 4 a shingle and 396 at 6. A 7,200-count box covers about 27 squares at 4 nails or 18 at 6, before starter and cap.