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Roofing Calculator,
squares, shingles & materials.
Enter your building footprint, roof pitch, and overhang to instantly calculate the number of roofing squares, shingle bundles, underlayment rolls, ridge cap, starter strip, and drip edge needed , for gable, hip, or shed roofs, in imperial or metric.
Inputs
Roof dimensions
Two slopes from a central ridge, the most common residential style.
Units
Roof pitch
26.6° · ×1.118 multiplier
Rule of thumb: 10–15%. Add more for complex dormers or valleys.
Examples
Gable roof
US units · 6:12 pitch
21.4squares
18.6 net · +15% waste · 1,860 sq ft
Footprint
1,664 sq ft
Net roof area
1,860 sq ft
Net squares
18.6
With 15% waste
21.39
Material estimate
What to order
| Material | Qty | Coverage / note |
|---|---|---|
| Shingle bundles | 65 bundles | 3 bundles per square (3-tab or architectural) |
| 15 lb felt underlayment | 6 rolls | ~400 sq ft / roll · 2,139 sq ft needed |
| Synthetic underlayment | 3 rolls | ~1,000 sq ft / roll (alt. to felt) |
| Ridge cap | 2 bundles | 52 lf · 35 lf / bundle |
| Starter strip | 1 bundles | 104 lf eave · 105 lf / bundle |
| Drip edge | 176 lf | Perimeter of all roof edges. Verify on-site |
These quantities are estimates based on standard industry coverage figures. Always verify with your material supplier and adjust for complex features like dormers, valleys, and skylights.
Roofing guide
How to calculate roofing materials — squares, pitch, and waste.
A roofing estimate starts with one key number: the roofing square. One roofing square equals 100 square feet of sloped roof surface. Every material quantity — shingles, underlayment, ridge cap, starter strip — is expressed in terms of squares. Getting this number right means you order enough without paying for excess.
What is a roofing square?
A roofing square is a unit of measurement equal to 100 square feet of roof surface area. It is used throughout the North American roofing industry to standardize material ordering. If your roof has 1,800 sq ft of surface area, you need 18 squares of materials.
Most residential shingles, both 3-tab and architectural (laminated) — are sold in bundles, with 3 bundles equaling 1 square. Each bundle covers approximately 33.3 sq ft. Some heavy architectural shingles require 4 bundles per square; always check the product label.
The pitch multiplier: how slope increases your roof area
A flat roof covering a 30×50 ft building has 1,500 sq ft. A sloped roof over the same footprint has more surface area, because the shingles travel farther as they climb the slope. The pitch multiplier converts your building's horizontal footprint into actual sloped surface area:
For a 6:12 pitch (very common in residential construction), the multiplier is √(36 + 144) / 12 = √180 / 12 ≈ 1.118. A 1,500 sq ft footprint becomes 1,500 × 1.118 = 1,677 sq ft of sloped roof, about 16.8 squares.
Pitch multiplier reference table
| Pitch | Angle | Multiplier | Area gain vs flat |
|---|---|---|---|
| 1:12 | 4.76° | 1 | +0% |
| 2:12 | 9.46° | 1.01 | +1% |
| 3:12 | 14.04° | 1.03 | +3% |
| 4:12 | 18.43° | 1.05 | +5% |
| 5:12 | 22.62° | 1.08 | +8% |
| 6:12 | 26.57° | 1.12 | +12% |
| 7:12 | 30.26° | 1.16 | +16% |
| 8:12 | 33.69° | 1.2 | +20% |
| 9:12 | 36.87° | 1.25 | +25% |
| 10:12 | 39.81° | 1.3 | +30% |
| 11:12 | 42.51° | 1.36 | +36% |
| 12:12 | 45° | 1.41 | +41% |
A 6:12 pitch row is highlighted. It is the most common residential pitch in the United States, offering a good balance between drainage, attic space, and material cost.
Waste factor: why you always order more
Shingles are cut at every valley, hip, ridge, eave, and rake. Cuts generate offcuts that cannot be reused elsewhere. A waste factor accounts for this loss so you do not run short:
- Simple gable roof: 10–15% waste. Two rectangular planes with minimal cuts.
- Hip roof: 15–20% waste. Four slopes mean four sets of diagonal hip cuts.
- Complex roof (dormers, multiple valleys): 20–25%. Every change of direction creates additional cut waste.
The waste factor also absorbs measurement errors, damaged shingles, and future repair needs. Order at least one extra bundle beyond the rounded-up total and store it for color-matched repairs.
Gable, hip, and shed roofs — what's the difference?
| Type | Description | Pros | Cons |
|---|---|---|---|
| Gable | Two rectangular slopes meeting at a central ridge | Simple, inexpensive, good attic ventilation | Less wind resistant; exposed triangular gable walls |
| Hip | Four slopes, two trapezoidal, two triangular, meeting at a ridge | Very wind resistant; self-bracing structure | More complex; more materials; less attic space |
| Shed | Single slope from high wall to low wall | Simplest build; modern look; easy to add skylights | Limited pitch range; less attic space; needs careful drainage planning |
Roofing materials at a glance
| Material | Coverage per unit | Purpose |
|---|---|---|
| Shingle bundle (3-tab / arch.) | ~33.3 sq ft · 3 bundles/square | Primary weatherproof surface layer |
| 15 lb felt underlayment | ~400 sq ft / roll | Secondary water barrier under shingles |
| Synthetic underlayment | ~1,000 sq ft / roll | Lighter, more tear-resistant alternative to felt |
| Ridge cap bundle | 35 linear feet / bundle | Seals the ridge line; specialized pre-bent shingles |
| Starter strip bundle | ~105 linear feet / bundle | First course at eave; seals shingle tabs down |
| Drip edge | 10 ft sections (sold by piece) | Metal flashing at eaves and rakes, directs water off roof |
Using metric measurements
This calculator accepts lengths in metres when you select Metric mode. The same pitch multiplier formula applies (rise is still expressed as rise-per-12 run — a universal notation). Area is shown in both square feet and square metres. Note that “roofing squares” (100 sq ft = 9.29 m²) is a North American industry term; outside the US and Canada, materials are sold per square metre. Multiply the shown square metres by your local coverage rate to get the bundle or roll count.