Roofing Calculator

Calculate roofing materials including shingles, underlayment, and ridge caps. Accounts for roof pitch, waste factors, and code requirements.

Professional Roofing Materials Calculator

Industry-standard calculations based on IRC, IBC, and manufacturer specifications

Roof Dimensions

feet
feet

Material Specifications

Ventilation (Required)

sq ft

Required for IRC ventilation compliance. Typically equals footprint (length × width).

Ridge Details

feet

All roofs have a ridge. For simple gable roofs, typically equals roof length.

Ready to Calculate

Enter your roof specifications and click "Calculate Materials" to see results

Based on NRCA standards, IRC/IBC codes, and manufacturer specifications from GAF, CertainTeed, Owens Corning, and IKO

Frequently Asked Questions

What is a roofing square?

One roofing square equals 100 square feet of roof surface. This is the standard industry measurement for estimating materials and labor. A 2,000 square foot roof equals 20 roofing squares. Most shingles are sold in bundles, with 3 bundles covering one roofing square.

How does roof pitch affect material calculations?

Roof pitch multiplies flat roof area to get actual surface area. A 6/12 pitch has a multiplier of 1.118. A 12/12 pitch multiplies by 1.414. Example: 1,000 sq ft footprint with 8/12 pitch (1.202 multiplier) requires 1,202 sq ft of shingles. Steeper roofs need proportionally more material.

How many bundles of shingles do I need?

Standard three-tab or architectural shingles come 3 bundles per square. Calculate total squares (including waste), then multiply by 3. A 25-square roof with 10% waste (27.5 squares) requires 83 bundles. Ridge cap shingles are calculated separately: 1 bundle per 30-33 linear feet of ridge.

What waste factor should I use for roofing?

NRCA recommends 10% waste for simple roofs with few penetrations. Complex roofs with valleys, dormers, or hips require 15% waste. Roofs with multiple angles, turrets, or irregular shapes need 15-20% waste. This accounts for cuts, starter strips, and ridge cap coverage.

Industry Standards Referenced

Last verified: November 2025

National Roofing Contractors Association (NRCA) Standards(NRCA Guidelines)

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Comprehensive industry standards for residential and commercial roofing installation, materials, and best practices. Covers shingle application, underlayment requirements, flashing details, and ventilation specifications.

Key Requirements:

  • •Minimum 4-inch headlap for asphalt shingles (exposure)
  • •Six nails per shingle minimum (four for 3-tab, six for architectural)
  • •Nail placement: 1 inch from edges, proper penetration depth
  • •Starter course required at eaves and rakes
  • •Ice and water shield in valleys and eaves (cold climates)
  • •Proper ventilation: 1 sq ft per 150 sq ft attic space
Applies to:All residential asphalt shingle installations

International Residential Code (IRC) R905 - Roof Coverings(IRC 2021 Section R905)

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Building code requirements for roof covering materials, application methods, and structural requirements. Specifies minimum slopes, underlayment, flashing, and attachment standards.

Key Requirements:

  • •Asphalt shingles: Minimum 2:12 pitch (9.5 degrees)
  • •Underlayment required on all roof decks before shingles
  • •Ice barrier required in areas with average daily temp ≤ 25°F (January)
  • •Wind resistance: Class D minimum (90 mph), higher for coastal
  • •Impact resistance ratings in hail-prone areas
  • •Roof deck must be minimum 7/16 inch OSB or 1/2 inch plywood
Applies to:All residential roof installations subject to IRC

ASTM D3462 - Asphalt Shingles (Organic Felt)(ASTM D3462)

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Material specifications for organic felt-based asphalt shingles including weight, thickness, granule adhesion, and tear resistance standards.

Key Requirements:

  • •Minimum weight standards by shingle type
  • •Granule adhesion requirements for wind resistance
  • •Tear strength minimums for durability
  • •Water absorption limits for weather resistance
Applies to:Traditional organic-based asphalt shingles (less common now)

ASTM D7611 - Asphalt Shingles (Glass Fiber Reinforced)(ASTM D7611)

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Performance standards for modern fiberglass-reinforced asphalt shingles. Covers impact resistance, wind uplift resistance, and Class A fire rating requirements.

Key Requirements:

  • •Class A, B, or C fire resistance rating (A is highest)
  • •Wind resistance: Class D (90 mph), F (110 mph), H (150 mph)
  • •Impact resistance: Class 1-4 (4 is highest, hail resistant)
  • •Minimum tensile strength and tear resistance
Applies to:Modern fiberglass asphalt shingles (most common today)

IRC R806 - Roof Ventilation(IRC Section R806)

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Requirements for attic and roof ventilation to prevent moisture buildup, ice dams, and premature shingle failure. Balances intake and exhaust ventilation.

Key Requirements:

  • •Minimum 1/150 ratio: 1 sq ft vent per 150 sq ft attic space
  • •Can reduce to 1/300 if 50-80% is high ventilation (ridge vent)
  • •Balanced ventilation: Equal intake (soffit) and exhaust (ridge)
  • •Net free area (NFA) accounts for screen/louver restrictions
  • •Baffles required to maintain airflow at eaves
Applies to:All vented attic spaces under roof decks

Manufacturer Specifications and Warranties(Varies by Brand)

Shingle manufacturers provide specific installation instructions that must be followed to maintain warranty validity. Specifications vary by product line and may differ from code minimums.

Key Requirements:

  • •Nail count: Some architectural shingles require 6 nails per shingle
  • •Specific starter strip products required for warranty
  • •Underlayment type requirements (synthetic vs. felt)
  • •Maximum and minimum temperature ranges for installation
  • •High-wind applications may require additional adhesive strips
Applies to:Warranty compliance - always consult product installation guide

Standards Disclaimer: Standards and codes are subject to periodic updates. Always verify current requirements with local building authorities and professional engineers before beginning construction. Links provided are for reference only.

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Want to Learn More?

NRCA guidelines, pitch multipliers, shingle bundle coverage, underlayment specs, and IRC/IBC ventilation requirements.

Read the Roofing Squares Guide

How to Use This Calculator

  1. Measure roof area: Input roof dimensions in square feet.
  2. Enter roof pitch: Select pitch (4/12, 6/12, 8/12, etc.).
  3. Calculate ridges & hips: Enter linear feet if applicable.
  4. Review materials: See roofing squares, bundles, and accessories needed.

Roofing Material Standards

One roofing square = 100 sq ft. Standard 3-tab shingles: 3 bundles per square. Architectural shingles: 4 bundles per square. Add 10-15% waste per NRCA guidelines.