📐 Roof Pitch Calculator
Find your roof pitch from rise and run, an angle, the span and ridge height, a rafter or a slope %
Pick what you can measure, enter it, and get the pitch as x/12, the angle in degrees, the slope percentage and the roof area multiplier — with the nearest common pitch and what it means for roofing materials.
Smart Home Calculators — Roof Pitch Calculator — smartroofingcalculator.com/roof-pitch-calculator/ — printed
Each method gives the same pitch — use the one you can reach
Vertical drop measured from the level's 12 in mark (any unit)
Horizontal length of the level — 12 in is standard (same unit as rise)
Adds the sloped roof area and squares
Measure it yourself: pitch finders and measuring tools compared →
Next calculatorRoof Area CalculatorThe next calculator people use on this job.🛠️ How This Calculator Works
Every method turns your measurement into rise per 12 in of run. Rise and run: pitch = rise ÷ run × 12. Angle: pitch = 12 × tan(angle). Span and ridge height: the run is half the span, so pitch = height ÷ (span ÷ 2) × 12. Rafter and run: the rise is √(rafter² − run²). Slope %: pitch = % × 12 ÷ 100. From the pitch the calculator gets the angle (arctan(rise ÷ 12)), the slope % and the area multiplier √(rise² + 144) ÷ 12.
📐 Formula
Pitch = rise ÷ run × 12 | Pitch from angle = 12 × tan(θ) | Angle = arctan(rise ÷ 12) | Multiplier = √(rise² + 144) ÷ 12 | Hip factor = √(rise² + 288) ÷ 12📝 Example Calculation
A 28 ft wide house with the ridge 7 ft above the wall plate: • Run = 28 ÷ 2 = 14 ft • Pitch = 7 ÷ 14 × 12 = 6/12 • Angle = arctan(6 ÷ 12) = 26.57° • Multiplier = 1.118, so a 1,500 sq ft footprint is about 1,677 sq ft of roof (16.8 squares)
💡 Pro Tips from Roofers
- Measure on the roof plane itself, not on a fascia or gutter, and check two spots: additions and dormers are often a different pitch.
- A phone level is accurate to about ±0.5°, which is about ±0.1 in of rise per foot at common pitches — round to the nearest half-inch pitch.
- Use the multiplier on the footprint including overhangs in the roof square footage calculator to get squares and bundles.
- Below 2/12 shingles are not allowed (IRC R905.2.2) — see the minimum roof pitch calculator for every material.
- On anything steeper than 6/12 measure from the attic or the ground — a roof pitch finder makes it a one-person job.
❓ Frequently Asked Questions
How do I calculate my roof pitch?
Roof pitch is the rise in inches for every 12 inches of horizontal run. Hold a 12 in level flat against the roof (or the underside of a rafter), level it, and measure straight down from the 12 in mark to the roof surface. That measurement is the rise: 6 in means a 6/12 pitch. If your run is not 12, pitch = rise ÷ run × 12, so 9 in of rise over 18 in of run is also 6/12.
How do I find the pitch of my roof without getting on it?
Measure from the attic or the ground. In the attic, put a level against a rafter and measure the rise over 12 in, or read the angle with a phone level and convert it (pitch = 12 × tan(angle)). From outside, measure the building span wall to wall and the ridge height above the top of the wall plate: pitch = ridge height ÷ (span ÷ 2) × 12. A 28 ft house with the ridge 7 ft above the plate is a 6/12.
How do I convert roof pitch to degrees?
Angle = arctan(rise ÷ 12). A 4/12 roof is 18.43°, 6/12 is 26.57°, 8/12 is 33.69°, 9/12 is 36.87° and 12/12 is exactly 45°.
How do I convert degrees to a roof pitch?
Rise = 12 × tan(angle). 30° gives 6.93/12, which is usually called a 7/12 pitch; 20° is 4.37/12 and 35° is 8.40/12. Enter the angle in the calculator to get the exact rise and the nearest common pitch.
What is the roof pitch multiplier and how do I use it?
The multiplier (pitch factor) is √(rise² + 144) ÷ 12: how much longer the sloped roof is than its flat run. Multiply the footprint, including overhangs, by it to get roof area. At 6/12 it is 1.118, so a 1,500 sq ft footprint has about 1,677 sq ft of roof, or 16.8 squares.
What is the most common roof pitch?
Most pitched roofs on US houses fall between 4/12 and 9/12, and 6/12 is the usual default on new construction plans. Ranch houses often sit at 4/12 to 5/12; older colonials, capes and houses in snow country are often 8/12 to 12/12.
What is the minimum roof pitch for shingles?
Asphalt shingles need at least 2/12 (IRC R905.2.2). From 2/12 up to 4/12 they must go over two layers of underlayment (IRC R905.1.1). Below 2/12 use a membrane such as TPO, EPDM or modified bitumen, or a standing seam metal panel rated for the slope.
What roof pitch is walkable?
Roofs up to about 6/12 can usually be walked with care in soft-soled shoes on a dry day; 7/12 and steeper need roof jacks, toe boards or a harness. For work rules, OSHA calls any roof over 4/12 a steep roof (29 CFR 1926.500(b)), which changes the fall-protection options for crews.
What is the difference between roof pitch and roof slope?
Today both usually mean rise over a 12 in run (6/12). In traditional carpentry, pitch was the rise divided by the full span, so a '1/4 pitch' roof is a 6/12 slope and a '1/3 pitch' is 8/12. Slope can also be written as a percentage: 6/12 is a 50% slope.
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How to find your roof pitch
Roof pitch is how many inches the roof rises for every 12 inches it runs horizontally, written as rise/12. A 6/12 roof climbs 6 in per foot: that is a 26.57° angle, a 50% slope and an area multiplier of 1.118. You can get it four ways, and all four give the same answer:
- Level and tape (on the roof or a rafter). Hold a 12 in level flat against the roof, level it, and measure straight down from the 12 in mark. The inches are the pitch.
- Phone level or angle finder. Lay the phone along a rafter in the attic or on the shingles and read the degrees; pitch = 12 × tan(angle).
- From the ground: span and ridge height. Measure the house wall to wall and the ridge height above the top of the wall plate (in the attic or on the gable end); pitch = height ÷ half the span × 12.
- From a rafter. Measure a rafter along its length and the horizontal run it covers; the rise is √(rafter² − run²).
Worked examples
Level and tape on the roof
Hold a 12 in level flat against the roof, level it, and measure straight down from its 12 in mark to the shingles: 6 in.
Pitch 6/12 · 26.57° · 50% · multiplier 1.1180
Phone level on a rafter
A phone level app laid along a rafter in the attic reads 30°.
Pitch 6.93/12 (call it 7/12) · 30.00° · 57.7% · multiplier 1.1547
Gable end: span and ridge height
The house is 28 ft wall to wall and the ridge sits 7 ft above the top of the wall plate (measure in the attic or on the gable end).
Pitch 6/12 · 26.57° · 50% · multiplier 1.1180
Rafter length and run
A rafter measures 16.77 ft along its top edge from the plate line to the ridge and covers a 15 ft run.
Pitch 6/12 · 26.56° · 50% · multiplier 1.1180
Roof pitch chart: degrees, slope and multiplier
The pitches houses are actually built with. For every pitch from 1/12 to 24/12 see the full roof pitch chart.
| Pitch | Angle | Slope | Multiplier |
|---|---|---|---|
| 1/12 | 4.76° | 8.3% | 1.0035 |
| 2/12 | 9.46° | 16.7% | 1.0138 |
| 3/12 | 14.04° | 25% | 1.0308 |
| 4/12 | 18.43° | 33.3% | 1.0541 |
| 5/12 | 22.62° | 41.7% | 1.0833 |
| 6/12 | 26.57° | 50% | 1.1180 |
| 7/12 | 30.26° | 58.3% | 1.1577 |
| 8/12 | 33.69° | 66.7% | 1.2019 |
| 9/12 | 36.87° | 75% | 1.2500 |
| 10/12 | 39.81° | 83.3% | 1.3017 |
| 12/12 | 45.00° | 100% | 1.4142 |
| 14/12 | 49.40° | 116.7% | 1.5366 |
| 18/12 | 56.31° | 150% | 1.8028 |
What your pitch means for the roof
- Under 2/12: a low-slope roof. Asphalt shingles are not allowed (IRC R905.2.2); use a membrane — see the flat roof calculator.
- 2/12 to under 4/12: shingles are allowed over two layers of underlayment (IRC R905.1.1) — see the underlayment calculator.
- 4/12 to 9/12: conventional pitch; every common material fits. Above 4/12 OSHA treats it as a steep roof for crews (29 CFR 1926.500(b)).
- Over 9/12: steep. Plan roof jacks and a harness, more waste and a higher labor rate — the labor hours calculator adjusts for pitch.
Once you know the pitch, multiply the footprint by the multiplier in the roof square footage calculator, then order with the shingle calculator. Framing a roof? The rafter calculator and the roof truss calculator start from the same pitch. For the pitch factor alone, see the roof pitch factor calculator; to convert an angle, the roof pitch to degrees page.
🔗 Related Roofing Calculators
- Roof Pitch Chart & Multiplier Table — Degrees and multiplier for 1/12 to 24/12
- Roof Pitch Factor Calculator — Slope factor for any rise and run
- Roof Square Footage Calculator — Footprint × multiplier = roof area and squares
- Minimum Roof Pitch Calculator — Which materials your pitch allows
- Rafter Calculator — Rafter length, birdsmouth and plumb cut
- Roof Height Calculator — Ridge height from span and pitch
· Reviewed by the Smart Home Calculators editorial team