ProjectCalc (working name)

Roofing Calculator

Shingle squares and bundles from your roof's footprint and pitch — plus underlayment, drip edge, ridge cap and nails.

Feet — include overhangs
Feet — include overhangs
Don't know it? Measure rise over a 12″ run in the attic or with a phone level app

ItemAmount
Roof area
Squares (100 sq ft each)
Shingle bundles (3 per square)
Starter bundles
Ridge cap bundles
Underlayment rolls (synthetic, ~1,000 sq ft)
Drip edge (10-ft pieces)
Roofing nails

This figures a simple two-slope roof from footprint + pitch. Dormers, valleys and multiple roof sections each add area — measure and run each section, then add the results.

🛒 Shopping list

ItemQty
Architectural shingles
Starter strip bundles
Ridge cap bundles
Synthetic underlayment rolls
Ice & water shield (eaves/valleys — 2-ft roll coverage)
Drip edge, 10-ft
Roofing nails, 1-1/4″

✅ Project checklist

  • Fall protection first — harness, roof jacks and a second person on site
  • Tear off to the deck (don't roof over two layers); inspect and replace bad decking
  • Ice & water shield at eaves (to 24″ inside the wall line) and in valleys
  • Drip edge: under underlayment at eaves, over it at rakes
  • Starter strip, then shingles from the bottom up, chalk lines every few courses
  • Ventilate: ridge vent + cap; seal every exposed nail head

How the math works

True roof area = footprint area × the pitch factor (the slope stretches the surface: a 6/12 roof has ~12% more area than its footprint). A "square" is 100 sq ft of finished roof; architectural shingles run 3 bundles per square. Waste: 10% for a plain gable, 15% for hip roofs with their angled cuts.

For estimation only. Follow the shingle manufacturer's coverage and nailing specs, and your local code for ice-barrier and underlayment requirements.