How do I calculate roof pitch?

Pitch = Rise ÷ Run × 12. Measure the rise (vertical) and run (horizontal distance, half the building width). Example: a roof that rises 5 feet over a 10-foot run = 5 ÷ 10 × 12 = 6:12 pitch. Or hold a level horizontally against the rafter and measure the rise at the 12-inch mark.

What is the most common roof pitch for houses?

4:12 to 6:12 is the most common range for residential roofing in the US. 4:12 is a popular low-conventional slope — adequate for asphalt shingles and most materials. 6:12 is steeper and provides better drainage. Steeper pitches (8:12+) are common in high-snow or traditional architectural styles.

What pitch is needed for asphalt shingles?

Standard asphalt shingles require a minimum 4:12 pitch. With a double layer of underlayment and manufacturer-approved low-slope application, 3:12 is the minimum. Below 3:12, asphalt shingles are not appropriate — use a low-slope membrane system (TPO, EPDM, or modified bitumen).

How does roof pitch affect the number of shingles needed?

Steeper roofs have more actual surface area than flat (plan) area. Use the pitch multiplier: actual area = footprint × multiplier. For a 1,000 sq ft footprint at 8:12 pitch, actual area is 1,000 × 1.202 = 1,202 sq ft. Shingles are calculated per 100 sq ft (one 'square') — divide actual area by 100 and add 10% waste.

How do I convert roof pitch to degrees?

Degrees = arctan(rise ÷ 12). A 6:12 pitch = arctan(6/12) = arctan(0.5) = 26.6°. A 12:12 pitch = arctan(1) = 45°. Most smartphones have a calculator with arctan (inverse tangent) function, or use: Angle ≈ pitch ratio × 4.76 (rough approximation).

Roof Pitch Calculator: How to Measure, Calculate & Use Roof Pitch

Calculate roof pitch from rise and run. Understand pitch notation, how pitch affects material needs, which pitches work for different materials, and how to convert pitch to degrees.

Related Calculators

Roof Pitch Calculator
Calculate roof pitch ratio, slope percentage, angle and rafter length from rise, run and horizontal span.
Rafter Calculator
Calculate common rafter length from building width, roof pitch, and overhang.

What Roof Pitch Means

Roof pitch measures how steep a roof is — how many inches the roof rises for every 12 inches of horizontal distance (run). It's expressed as a ratio: rise : 12.

A 4:12 pitch rises 4 inches for every 12 inches of horizontal run
A 12:12 pitch rises 12 inches per 12 inches of run — a 45° angle

Calculating Pitch from Rise and Run

Pitch = Rise ÷ Run × 12

Example: A roof that rises 6 feet over a 12-foot horizontal span: - Pitch = (6 ÷ 12) × 12 = 6:12

If you have the total span (ridge to exterior wall, both sides): - Run = Total Span ÷ 2 - Example: 24-ft span → 12-ft run

Converting Pitch to Degrees

Angle (degrees) = arctan(Rise ÷ 12)

Pitch	Angle	Category
1:12	4.8°	Low slope
2:12	9.5°	Low slope
3:12	14.0°	Low slope
4:12	18.4°	Conventional
6:12	26.6°	Conventional
8:12	33.7°	Steep
12:12	45.0°	Steep

Roofing Material Requirements by Pitch

Pitch determines which roofing materials are appropriate:

Pitch	Minimum Slope for This Material
Flat membrane (TPO, EPDM)	1/4:12 to 1:12
Metal panels (standing seam)	1:12+
Asphalt shingles (standard)	4:12+ (3:12 with modified underlayment)
Wood shingles	4:12+
Slate	4:12+
Clay/concrete tile	4:12+
Metal shingles	3:12+

Below 4:12: Use low-slope roofing systems (TPO, EPDM, modified bitumen). Asphalt shingles on pitches below 3:12 will leak.

Pitch Multiplier for Material Quantity

The pitch multiplier converts flat (plan) area to actual roof surface area, accounting for the additional area created by slope:

Actual Roof Area = Plan (footprint) Area × Pitch Multiplier

Pitch	Multiplier
3:12	1.031
4:12	1.054
5:12	1.083
6:12	1.118
7:12	1.158
8:12	1.202
9:12	1.250
10:12	1.302
12:12	1.414

Example: A house with a 1,200 sq ft footprint and a 7:12 pitch: - Actual roof area: 1,200 × 1.158 = 1,390 sq ft (43.5 squares) - Shingles are sold by the "square" (100 sq ft). You'd need ~14–15 squares.

How to Measure Roof Pitch from a Ladder or the Attic

From a ladder (outside): Place a 12-inch level horizontally against a rafter. Measure 12 inches along the level from one end. Measure the vertical distance from the bottom of the level to the rafter at the 12-inch mark. That measurement is the rise — giving you X:12 pitch.

From the attic: Hold the level horizontally against the underside of a rafter. Use a tape measure to find the rise over 12 inches of horizontal distance.

Related Guides

Frequently Asked Questions

How do I calculate roof pitch?: Pitch = Rise ÷ Run × 12. Measure the rise (vertical) and run (horizontal distance, half the building width). Example: a roof that rises 5 feet over a 10-foot run = 5 ÷ 10 × 12 = 6:12 pitch. Or hold a level horizontally against the rafter and measure the rise at the 12-inch mark.
What is the most common roof pitch for houses?: 4:12 to 6:12 is the most common range for residential roofing in the US. 4:12 is a popular low-conventional slope — adequate for asphalt shingles and most materials. 6:12 is steeper and provides better drainage. Steeper pitches (8:12+) are common in high-snow or traditional architectural styles.
What pitch is needed for asphalt shingles?: Standard asphalt shingles require a minimum 4:12 pitch. With a double layer of underlayment and manufacturer-approved low-slope application, 3:12 is the minimum. Below 3:12, asphalt shingles are not appropriate — use a low-slope membrane system (TPO, EPDM, or modified bitumen).
How does roof pitch affect the number of shingles needed?: Steeper roofs have more actual surface area than flat (plan) area. Use the pitch multiplier: actual area = footprint × multiplier. For a 1,000 sq ft footprint at 8:12 pitch, actual area is 1,000 × 1.202 = 1,202 sq ft. Shingles are calculated per 100 sq ft (one 'square') — divide actual area by 100 and add 10% waste.
How do I convert roof pitch to degrees?: Degrees = arctan(rise ÷ 12). A 6:12 pitch = arctan(6/12) = arctan(0.5) = 26.6°. A 12:12 pitch = arctan(1) = 45°. Most smartphones have a calculator with arctan (inverse tangent) function, or use: Angle ≈ pitch ratio × 4.76 (rough approximation).

Last updated 7/28/2026