How do I measure roof pitch from the ground?

Use a speed square and level at the gable end, or measure 12 inches horizontally on the underside of a rafter and the vertical rise at that point. A 4/12 pitch means the roof rises 4 inches for every 12 inches of horizontal run — a common residential pitch.

What is a roofing square and why does it matter?

One roofing square equals 100 square feet of roof area. Shingles are sold by the square (typically 3 bundles per square for standard 3-tab, 4-5 for architectural). Calculating in squares lets you order materials confidently regardless of shingle type.

How much waste should I add for a complex roof?

Simple gable roofs need 5-10% waste. Roofs with multiple valleys, dormers, hips, or skylights need 12-18%. Always order an extra bundle or two for future repairs — matching dye lots years later is difficult, and leftover material ensures consistent appearance.

Can I overlay new shingles on top of old ones?

Building codes allow one layer of new shingles over one existing layer (maximum two total), but only if the existing roof is flat and in good condition. Overlaying saves disposal costs but shortens the new roof's lifespan and voids some manufacturer warranties.

Are the calculations on Roofing Calculator | Shingle & Material Estimator private?

Yes, completely. All calculations are performed entirely locally inside your browser using JavaScript. No inputs or personal metrics are ever transmitted to or stored on our servers.

Roofing Calculator | Shingle & Material Estimator

Roofing Calculator – Material EstimatorMetriova provides free online calculators for finance, business, health, and construction. Calculate loans, investments, fitness metrics, and project materials in seconds.Roofing Shingle Coverage and SquaresRoofing is measured in "squares" — one square equals 100 sq ft of roof area. Most asphalt shingle bundles cover 33.3 sq ft, so 3 bundles make one square. Always account for roof pitch: a 6/12 pitch increases surface area by ~12% compared to flat measurement. Add 10-15% extra for waste and valleys.

Roof Area (sq ft)

Squares Needed

Bundles (3 per square)

1,000

1,500

2,000

2,500