Roofing Calculator for a Garage
Estimate shingle bundles and squares for a garage roof.
Garage roofs are simple gable or hip layouts that go quickly. A standard two-car garage roof is 400–600 sq ft of surface — 4–6 squares. Match the shingle color and profile to the main house if the garage is visible from the street.
Squares
13.42
1,342 ft²
Shingle bundles
41
3 bundles / square
Underlayment rolls
4
400 ft² rolls
Save this project
Sign in to save calculations to your dashboard.
Download your PDF report & project guide
Your results and inputs, a printable shopping list, a step-by-step guide and pro tips — in one PDF.
Planning a whole project?
Get every calculator, a full shopping list and a budget template for:
Recommended tools & materials
Handy picks for this project on Amazon.
Roofing Nailer
Speed up shingle installation
View on Amazon →
Synthetic Roof Underlayment
Lightweight, tear-resistant
View on Amazon →
Roofing Safety Harness Kit
Stay safe on steep pitches
View on Amazon →
Utility Knife with Hook Blades
Cut shingles cleanly
View on Amazon →
As an Amazon Associate, MaterialCalc earns from qualifying purchases.
How does the roofing calculator work?
Roof area = house footprint × pitch factor. The pitch factor is √(1 + (rise/12)²): a 6:12 roof has a 1.118 factor. A "square" is 100 ft² of roof. Shingles are sold in 3 bundles per square.
Which guide explains this in more depth?
- Panel roofs waste differently from shingles: ribs, hips and valleys all change the number you order. Read the metal roofing calculator waste factor guide for the full worked example.
What else do people ask about this calculator?
How many bundles of shingles for a 2-car garage roof?
A 20×20 ft garage with a 6:12 pitch has ~450 sq ft of roof = 4.5 squares. That's 14 bundles of architectural shingles.
Same shingles on a detached garage?
If the garage is visible from the street, yes — matching shingles keep curb appeal. Detached garages hidden behind the house can use a cheaper 3-tab shingle to save money.
How many bundles of shingles do I need?
3 bundles per roofing square. For a 40×30 ft home with a 6:12 roof: about 13.4 squares × 3 = 41 bundles.
What is a roofing square?
100 ft² of roof surface. Shingles are priced per square and packaged in bundles that cover ~33 ft² each.
Which related calculators should I use next?
All calculators