Calculator
Shed Roof Pitch Calculator
Roof pitch is rise in inches per 12 in of run. A 4/12 roof rises 18.4 degrees. On an 8 ft wide gable shed, 4/12 puts the ridge 16 in above the wall plate and needs rafters about 4.2 ft long before the overhang. Asphalt shingles need at least 2/12, with double underlayment below 4/12.
Roof pitch calculatorUpdates as you type
4/12 = 18.4°
- Ridge height above walls
- 16.0 in
- Rafter length incl. overhang
- 4.74 ft
- Roof area
- 104 sq ft
- Shingle bundles (+10%)
- 4
- Roofing squares
- 1.04
Standard single underlayment is fine at this pitch.
Roofing, finishing and ventilation
Matched to this result, spread from budget to premium.
Prices change often; the button shows today's price on Amazon.
What is roof pitch?
Roof pitch is the vertical rise, in inches, for every 12 in of horizontal run. A 4/12 roof rises 4 in per foot, which is 18.4 degrees. Most kit sheds come with a fixed roof, so this calculator matters most when you build a wood shed, re-roof one, or compare how much snow a roof will shed.
Pitch to angle chart
| Pitch | Angle | Rafter factor | Roofing note |
|---|---|---|---|
| 2/12 | 9.5° | 1.014 | Shingle minimum, double underlayment |
| 3/12 | 14.0° | 1.031 | Double underlayment |
| 4/12 | 18.4° | 1.054 | Standard underlayment |
| 6/12 | 26.6° | 1.118 | Common on barn-style sheds |
| 8/12 | 33.7° | 1.202 | Sheds snow well |
| 12/12 | 45.0° | 1.414 | Steep, extra loft height |
The full table is on the roof pitch chart.
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Frequently asked questions
What is the minimum pitch for a shingle shed roof?
The International Residential Code (R905.2.2) allows asphalt shingles on slopes of 2/12 or steeper, and requires two layers of underlayment between 2/12 and 4/12. Below 2/12, use rolled roofing, metal panels rated for low slopes, or a membrane.
What pitch is best for a shed in snow country?
Steeper sheds snow better. Under the ASCE 7 method, a non-slippery roof on an unheated building gets no slope reduction until it passes about 45 degrees, while a smooth metal roof starts shedding load above about 15 degrees. A 6/12 to 8/12 metal roof is a practical choice where heavy snow is routine.
How many bundles of shingles for a shed?
Three bundles cover one 100 sq ft square. The calculator computes the sloped roof area including overhangs, adds 10 percent for waste and starter rows, and divides by 33.3 sq ft per bundle. An 8x10 gable shed at 4/12 with 6 in overhangs needs about 4 bundles.
This page is researched guidance, not professional engineering, legal or building-code advice. Sizes, loads and permit rules vary by product and by town: check your local code and the kit manufacturer's instructions before you build.