Roofing Calculator
Estimate everything you need to roof a house or building from one page: roofing squares, shingle bundles, underlayment rolls, ridge cap, starter strip, nails, waste, and total cost. The pitch-multiplier engine converts your flat footprint into true sloped roof area automatically — no manual conversions.
Example Projects
Ranch House
50' × 30' • 6/12 • Architectural
Two-Story Home
40' × 28' • 8/12 • Architectural
Metal Building
60' × 40' • 4/12 • Metal Panels
Re-Roof / Tear-Off
45' × 30' • 6/12 • Tear-Off On
Configure Roof View Results
Roofing Estimate
View Full Material Takeoff
| Footprint area | 0 ft² |
| Pitch multiplier | ×1.000 |
| Roofing squares (base) | 0.00 sq |
| Squares with waste | 0.00 sq |
| Ridge cap (ridge + hip) | — |
| Starter strip | 0 lf |
| Valley flashing | — |
| Fasteners | 0 nails |
How this was calculated:
Everything behind the Roofing Calculator
Formulas, reference charts, and detailed answers — expand any section you need.
Roof Pitch Multiplier Table
Roof pitch (rise over a 12-inch run) determines how much larger your actual roof surface is than the footprint below it. Multiply footprint area by the pitch multiplier to get true roof area. A steeper pitch needs more material.
| Roof Pitch | Approx. Angle | Multiplier |
|---|---|---|
| Flat (0/12) | 0° | 1.000 |
| 3/12 | 14° | 1.031 |
| 4/12 | 18.4° | 1.054 |
| 6/12 | 26.6° | 1.118 |
| 8/12 | 33.7° | 1.202 |
| 9/12 | 36.9° | 1.250 |
| 10/12 | 39.8° | 1.302 |
| 12/12 | 45° | 1.414 |
The exact formula is multiplier = √(rise² + 12²) ÷ 12. The calculator applies it automatically when you pick a pitch.
Shingle Bundles Per Square by Material
Roofing is priced by the square (100 sq ft). How many purchase units cover one square depends on the material. These are the defaults the calculator fills in — all editable to match your exact product.
| Material | Units Per Square | Notes |
|---|---|---|
| 3-Tab Shingles | 3 bundles | ~80 shingles per square |
| Architectural / Dimensional | 3–4 bundles | Heavier premium lines use 4 |
| Metal Panels | Panel-based | Varies by panel size & overlap |
| Clay / Concrete Tile | 90–110 pieces | Depends on tile exposure |
| Membrane (TPO / EPDM) | By roll | Sold in large sheets |
Roofing Waste Percentage Guide
Always order extra material for cuts, overlaps, and mistakes. Roof complexity drives how much:
| Roof Complexity | Recommended Waste |
|---|---|
| Simple gable roof | 10% |
| Roof with hips or valleys | 15% |
| Complex / cut-up roof | 20% |
| Metal panels | 5–10% |
Underlayment Roll Coverage
Underlayment goes down before the shingles. Coverage per roll already allows for the standard overlap:
| Underlayment Type | Coverage Per Roll |
|---|---|
| 15 lb Felt | ~4 squares |
| 30 lb Felt | ~2 squares |
| Synthetic | ~10 squares |
Roofing Calculator: How Many Shingles Do I Need?
Your roof area isn't the same as your house's footprint — a sloped roof always has more surface than the ground it covers. To calculate shingles needed: multiply footprint (length × width) by your pitch multiplier to get actual roof area, divide by 100 for roofing squares, then multiply by bundles-per-square for your shingle type (3 for 3-tab, 3–4 for architectural).
Example: a 1,500 sq ft footprint at 6/12 pitch has a multiplier of 1.118, giving about 1,677 sq ft of actual roof — roughly 16.8 roofing squares. At 3 bundles per square with 10% waste, that's about 55–56 bundles of architectural shingles.
What Is a Roofing Square?
One roofing square equals 100 square feet of roof area. It's the standard unit contractors and suppliers use to price shingles, underlayment, and labor — most roofing quotes are "per square," not per square foot. A 2,000 sq ft roof is 20 squares. Knowing your square count is the fastest way to compare quotes and order the right amount of material.
Ridge Cap, Starter Strip & Nails: The Extras Most Calculators Miss
A complete roof needs more than field shingles. This calculator also estimates the parts many tools ignore:
- Ridge cap covers the ridge and hips. Enter those linear feet and it estimates cap bundles (about 25 linear feet per bundle).
- Starter strip runs along the eaves and rakes — roughly your roof perimeter, at about 100 linear feet per bundle.
- Nails are estimated at 4 per shingle (about 320 per square), or 6 per shingle (480 per square) in high-wind areas, and converted to pounds.
- Metal roofs use screws instead — roughly 80 per square along the panel ribs.
Metal Roofing Calculator Basics
Metal roofing is estimated by panel, not bundle. Divide actual roof area by a single panel's coverage, accounting for overlap. Fasteners are typically screws spaced every 12–24 inches along the panel ribs — roughly 80 per square. Waste is lower than shingles, usually 5–10%, because panels are cut to length. Switch the calculator to Metal mode and it sets these defaults automatically, then lets you fine-tune panels-per-square for your manufacturer.
Roofing Cost Calculator
Roofing cost depends on material type, roof size, pitch, complexity, and local labor rates. Material is usually priced per square; labor may be quoted per square or as a flat rate, and rises for taller buildings. Tear-off adds removal and disposal costs when you're replacing an existing roof. Turn on "Estimate Cost & Budget" to combine material, labor, tear-off, and delivery into a single total — in your choice of 150+ currencies.