Asphalt Shingle Calculator
An asphalt shingle reroof needs more than just bundles. You also need underlayment, starter strip, ridge cap, drip edge, and the right number of nails for your roof pitch. This calculator takes your roof footprint, pitch, shingle type, and ridge and eave lengths and returns every quantity in one pass. We use the standard 100 sq ft roofing square, account for the slope multiplier so steep roofs get the right bundle count, and switch to 6-nail patterns above a 9/12 pitch where IRC R905 requires it. Use it to price a job, build a shopping list, or sanity-check a contractor's estimate.
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- Updated 2026-04-29
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Length of your roof footprint
Width of your roof footprint
Rise over run (e.g., 6/12 means 6" rise per 12" run)
Premium shingles are heavier and cover less per bundle
Total linear feet of ridge and hips that need ridge cap
Total linear feet of eaves (for starter strip)
10-12% for simple gables, 15-20% for hips, dormers, and valleys
Visual Preview
Fill in the form to see your estimate.
How It's Calculated
1. Footprint Area = Length × Width 2. Actual Roof Area = Footprint × Pitch Multiplier (1.003 to 1.414) 3. Total Area = Actual Roof Area × (1 + Waste Factor) 4. Squares = Total Area ÷ 100 5. Shingle Bundles = Total Area ÷ coverage per bundle 6. Underlayment Rolls = Total Area ÷ 400 7. Starter Bundles = Eave Length ÷ 100 8. Ridge Cap Bundles = (Ridge + Hip Length) ÷ 35 9. Nails = Squares × 320 (or 480 if pitch ≥ 9/12)
Worked Examples
A 1,500 sq ft footprint at 6/12 pitch gives 1,677 sq ft of actual area. With 12% waste = 1,878 sq ft, or 18.8 squares. You need 57 bundles of architectural shingles, 5 underlayment rolls, 1 starter bundle, 2 ridge cap bundles, and 50 lbs of nails.
480 sq ft footprint × 1.414 pitch × 1.15 waste = 781 sq ft. Premium shingles at 25 sq ft per bundle means 32 bundles. Steep pitch triggers the 6-nail pattern, so figure ~31 lbs of nails.
1,400 sq ft footprint × 1.202 × 1.18 = 1,985 sq ft of total area. That is 60 bundles plus 3 ridge cap bundles for the long combined ridge and hip runs. The 18% waste covers extra cuts at every hip ridge and around dormer flashings.
Assumptions & Waste Factor
- Coverage of 33.3 sq ft per bundle for 3-tab and architectural shingles, 25 sq ft per bundle for premium
- One roofing square equals 100 square feet
- Underlayment rolls cover 400 sq ft (standard 15 lb felt with overlap)
- Starter strip bundles cover ~100 linear feet of eave
- Ridge cap bundles cover ~35 linear feet of ridge or hip
- 4 nails per shingle below 9/12 pitch, 6 nails per shingle at 9/12 and above (IRC R905.2.5)
- Footprint dimensions are the horizontal area beneath the roof, not the slope distance
Use 10-12% waste for simple gable roofs with full-length runs. Hip roofs add diagonal cuts at every corner — start at 15%. Add another 5% for dormers, valleys, skylights, or steep pitches above 9/12 where shingles are harder to align. Premium and designer shingles often need 15% even on simple roofs because pattern matching wastes more material.
Frequently Asked Questions
How many bundles of shingles are in a square?
Standard 3-tab and architectural shingles take 3 bundles per 100 sq ft square. Premium and designer shingles are heavier, so they often take 4 bundles per square. Always confirm coverage on the bundle wrapper before ordering.
What is the difference between 3-tab and architectural shingles?
3-tab shingles are flat, single-layer, and last 15 to 20 years. Architectural (also called dimensional or laminated) shingles are thicker, have a layered look, and last 25 to 30 years. Both cover 33.3 sq ft per bundle.
Why do steep roofs need more nails?
IRC R905.2.5 requires 6 nails per shingle on roofs with a pitch of 9/12 or steeper because gravity and wind uplift put more strain on the fasteners. Below 9/12 the standard is 4 nails per shingle.
Can I install asphalt shingles on a low-slope roof?
Asphalt shingles need at least a 2/12 pitch, and pitches between 2/12 and 4/12 require a double layer of underlayment per IRC R905.1.1. Below 2/12, use a membrane system like TPO, EPDM, or modified bitumen instead.
How much underlayment do I need?
One roll of standard 15 lb asphalt-saturated felt covers about 400 sq ft after overlap. Synthetic underlayment rolls vary from 1,000 to 2,000 sq ft per roll, so check the label and divide your total area by that number.
Do I need ice and water shield separately?
Yes. Ice and water shield is required at eaves, valleys, and around penetrations in cold climates. It is not the same as field underlayment. Plan on covering the first 3 to 6 feet up from each eave plus all valleys.
How do I measure ridge and hip length?
Walk the roof or use satellite imagery. Sum every ridge run and every hip line. A simple gable usually has one ridge equal to the building length. A hip roof has 4 hip lines plus a shorter top ridge.
Should I include nails in my shopping list?
Yes. A pound of 1.25 inch roofing nails contains roughly 120 nails. Buy by the pound rather than counting individual nails. Most pros keep an extra 10 to 20 percent on hand to avoid mid-job runs to the supplier.
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Disclaimer: This calculator provides estimates for planning purposes only. Actual material requirements may vary based on site conditions, installation methods, and other factors. Always consult with a qualified professional before making purchasing decisions.