Roofing calculator: squares and shingle bundles
Enter the footprint and pitch, or the roof area if you already have it. You get squares, bundles, underlayment, ridge cap, drip edge and a rough job price. Everything stays in your browser.
Your estimate
- Roof area (before waste)
- —
- Pitch factor
- —
- Area with waste
- —
- Squares (100 sq ft each)
- —
- Shingle bundles (3 per square)
- —
- Underlayment
- —
- Ridge cap
- —
- Drip edge (+5% overlap)
- —
- Shingle cost
- —
- Labor (rough)
- —
- Rough job total
- —
Estimates only. Bundles per square, roll coverage and ridge cap coverage vary by product; check the wrapper. From the footprint, drip edge uses the plan perimeter and runs a little short on steep rakes. Starter strip, flashing, vents, nails and tear-off are not included.
How to measure a roof from the ground
- Measure the length and width of the building at the walls, in feet, and add the overhang.
- Find the pitch: the inches the roof rises for every 12 inches it runs. A pitch gauge or a level and tape on the rake works; so do the plans.
- The calculator multiplies the footprint by the pitch factor to get the sloped area. For roofs with many sections, add up each section or use an aerial report and enter the roof area directly.
- Pick a waste factor that fits the roof: more hips, valleys and dormers mean more cutting.
Pitch multipliers and shingles for a 1,500 sq ft footprint
Multiplier = √(1 + (rise ÷ 12)²). No overhang, 10% waste, 3 bundles per square. Computed with the same formula as the calculator above.
| Pitch | Multiplier | Roof area | Squares (+10%) | Bundles |
|---|---|---|---|---|
| 3/12 | × 1.031 | 1,546 sq ft | 17.0 | 52 |
| 4/12 | × 1.054 | 1,581 sq ft | 17.4 | 53 |
| 5/12 | × 1.083 | 1,625 sq ft | 17.9 | 54 |
| 6/12 | × 1.118 | 1,677 sq ft | 18.4 | 56 |
| 7/12 | × 1.158 | 1,737 sq ft | 19.1 | 58 |
| 8/12 | × 1.202 | 1,803 sq ft | 19.8 | 60 |
| 9/12 | × 1.250 | 1,875 sq ft | 20.6 | 62 |
| 10/12 | × 1.302 | 1,953 sq ft | 21.5 | 65 |
| 12/12 | × 1.414 | 2,121 sq ft | 23.3 | 71 |
Squares and bundles
Roofers count in squares: one square covers 100 square feet of roof. Most 3-tab and architectural shingles come three bundles to a square, but some heavier products need four or more, so check the wrapper.
What this calculator leaves out
Starter strip, ice and water shield, step and valley flashing, vents, pipe boots, nails, tear-off, disposal and permits are not included. Follow the shingle maker’s installation instructions and your local code.
Questions
How many squares is a 2,000 sq ft roof?
Twenty squares before waste. With 10% waste it is 22 squares, which is 66 bundles of a three-bundle-per-square shingle.
What is a pitch factor?
It turns the flat footprint into the real sloped area. A 6/12 roof has a factor of about 1.118, so a 1,000 sq ft footprint has about 1,118 sq ft of roof. Steeper roofs have bigger factors.
How much waste should I add for shingles?
Around 10% is common for a simple gable roof. Hip roofs and roofs with valleys and dormers often need 15% or more because of extra cutting.
How many rolls of underlayment do I need?
It depends on the product. Many synthetic rolls cover about 10 squares, #15 felt about 4 squares and #30 felt about 2 squares. Pick yours above and check the roll label.
Is this calculator free? Does it save my numbers?
Yes, it is free and needs no sign-up. Nothing is saved or sent anywhere; the math runs in your browser and is gone when you close the page.
Turn this into a quote in about 60 seconds with SpeakBid
Talk through the job in English or Spanish and SpeakBid fills in the line items, tax and total.
Coming soon to the App Store and Google Play. New subscribers get a 14-day free trial of Pro.
Your win is our win.