Roofing: squares, bundles, pitch and gutters
Roofing is measured in squares of 100 square feet, and asphalt shingles usually come three bundles to the square. A 40 x 30 ft house with a 6/12 roof and 12 inch overhangs has 15.0 squares of roof; with 10% waste that is 50 bundles of shingles. The pitch matters because a steeper roof has more surface over the same footprint.
This page collects every roofing calculator and guide we have: squares and bundles, pitch and rafters, metal panels, underlayment and ice and water shield, attic ventilation and gutters.
Shingle bundles by house size and pitch
Gable roof, 12 inch overhangs, 10% waste, three bundles per square. Worked out by the roofing calculator from the house footprint.
| Footprint (feet) | 4/12 pitch | 6/12 pitch | 8/12 pitch | 10/12 pitch |
|---|---|---|---|---|
| 30 x 20 | 25 | 26 | 28 | 31 |
| 40 x 25 | 40 | 42 | 45 | 49 |
| 40 x 30 | 47 | 50 | 54 | 58 |
| 50 x 30 | 58 | 62 | 66 | 72 |
| 60 x 30 | 70 | 74 | 79 | 86 |
| 60 x 40 | 91 | 97 | 104 | 112 |
Squares, bundles and the whole re-roof list
Start with the roofing calculator for squares and bundles, then use the replacement list for the rest: underlayment, starter strip, ridge cap, drip edge and nails. Hips, valleys and dormers add waste, so use 15% on a cut-up roof.
Pitch and rafters
Pitch is rise over 12 inches of run. A 6/12 roof rises 6 inches per foot, which is 26.6 degrees and adds about 12% to the area over the flat footprint. The rafter calculator turns span and pitch into rafter length.
Metal roofing
Metal panels are counted per side from the roof length and panel coverage width, and ordered cut to the slope length. The metal roofing calculator also gives trim lengths for the ridge, eaves and rakes.
Underlayment, ventilation and gutters
In cold climates, ice and water shield runs up from the eaves past the inside of the wall line. A roof also needs balanced intake and exhaust ventilation, and gutters sized to the roof that drains into them.
Every calculator for this topic
Guides
- Common Mistakes When Replacing a Shingle Roof (Squares, Pitch)Roof mistakes: measuring the footprint, not the slope, and too little waste. A 40 × 30 ft house at 6/12 pitch is 15.0 squares and 50 bundles of shingles.
- How Many Bundles of Shingles for 1,000 Square Feet?1,000 square feet of roof is 10 squares, which takes 30 bundles of shingles before waste and 33 with 10% extra. Bundles for 500 to 3,000 sq ft.
- How Much Gutter Do I Need? Sections, Hangers and Downspouts60 ft of 5 inch gutter takes 6 sections of 10 ft, 32 hangers and a slope of 1.5 inches. Charts of parts by run and downspout height.
- Roof Pitch Chart: Pitch, Angle, Slope Percent and Roof Area FactorA 6/12 roof pitch is an angle of 26.6° and a 50% slope, and adds 12% to the area of the footprint. A chart of every pitch from 1/12 to 12/12.
- What Size Extension Ladder Do I Need? Height and Reach ChartA 28 ft extension ladder reaches a roof edge 21 ft up. Charts of the ladder size for each height, the base distance and the 4 to 1 rule.
- How Much Metal Roofing Do I Need? Panels, Length and TrimHow many metal roofing panels and how long, plus ridge cap and trim, for a gable roof? Charts by building size and pitch, with how to measure and order.
- Ice and Water Shield: How Much Do I Need? Rolls by Eave and PitchHow many rolls of ice and water shield for eaves, valleys and penetrations? A chart by roof pitch and eave length, the code rule, and how to install it.
- Rafter Length Chart: Common Rafters by Span and PitchA chart of common rafter lengths by building width and roof pitch, how to calculate rafter length with overhang, the roof angle, and how many rafters you need.
- Roof Replacement Materials List: Shingles, Underlayment and VentsWhat to buy to re-roof a 30×40 ft house at a 6/12 pitch: shingle bundles, underlayment, drip edge, nails and vents, with a chart for other house sizes.
- How Much Attic Ventilation Do I Need? The 1:150 and 1:300 RulesHow to calculate attic ventilation in square inches of net free area, split between intake and exhaust, with a chart for common attic sizes and ridge vents.
- How to Calculate Roofing Squares (and Bundles of Shingles)One roofing square is 100 sq ft of roof. A 40 × 30 ft house with a 6/12 pitch has 15.0 squares: 50 bundles of shingles with 10% waste.
Other guides that use these calculators: How Many Bundles of Ridge Cap Shingles Do I Need? · How Much Drip Edge Do I Need? Pieces for Eaves and Rakes · How Much Soffit Do I Need? Vinyl Panels and Channel · How to Measure Attic Insulation Depth and Work Out the R-Value · What Size Attic Fan Do I Need? CFM by Attic Size and Intake · How Many Sheets of Plywood Do I Need? 4x8 Sheets by Area · How Much Insulation Should Be in the Attic? R-Value and Inches
Answers for common sizes
Already know the size? These pages give the worked answer for one common size each, with the inputs filled in so you can adjust them.
Project planners
Planning the whole job rather than one material? These step-by-step planners put the calculators above in the order you will need them.
Frequently asked questions
How many bundles of shingles are in a square?
Three for most architectural and three-tab shingles, and four for some heavier products. The wrapper says how much each bundle covers.
How many squares is a 40 x 30 house roof?
About 15.0 squares at a 6/12 pitch with 12 inch overhangs, or 50 bundles with 10% waste.
How much waste should I add for shingles?
Ten percent for a simple gable roof, 15% for hips, valleys and dormers. Starter strip and ridge cap are counted separately.
Do I need ice and water shield?
Where the code calls for it, usually in places with freezing winters: along the eaves, in valleys and around penetrations.
Related topics
Estimates only. Quantities depend on your materials, site and supplier, so check coverage and sizes on the label. Follow local building codes for anything structural. How we calculate.