# Roof Pitch Calculator

> This roof pitch calculator converts pitch to angle and percent slope, then uses the slope multiplier to turn your footprint into real roof area.

**Quick answer:** A 6:12 roof rises 6 inches for every 12 inches of run: a 26.57° angle, a 50% slope and a 1.118 area multiplier. A 1,500 sq ft footprint therefore has about 1,677 sq ft of roof, or 16.8 squares of shingles, before waste.

_Last updated: October 3, 2026. Estimates only; confirm quantities with your supplier._

## How to calculate roof pitch

Roof pitch is how steep a roof is, written as rise over run, almost always over a 12 inch run in the U.S. A 6:12 roof rises 6 inches for every 12 inches of horizontal distance. The same slope can be an angle in degrees or a percent grade.

```
angle = arctan(rise ÷ 12)
percent slope = rise ÷ 12 × 100
slope multiplier = √(rise² + 144) ÷ 12
roof area = footprint × multiplier
```

Example: 6:12 gives arctan(0.5) = **26.57°**, a **50%** slope and a multiplier of √(36 + 144) ÷ 12 = **1.118**. A 1,500 sq ft footprint is **1,677 sq ft** of roof, which is 16.8 squares.

### Pitch chart

| Pitch | Angle | Slope | Area multiplier |
| --- | --- | --- | --- |
| 2:12 | 9.5° | 16.7% | 1.0138 |
| 3:12 | 14.0° | 25.0% | 1.0308 |
| 4:12 | 18.4° | 33.3% | 1.0541 |
| 5:12 | 22.6° | 41.7% | 1.0833 |
| 6:12 | 26.6° | 50.0% | 1.1180 |
| 7:12 | 30.3° | 58.3% | 1.1577 |
| 8:12 | 33.7° | 66.7% | 1.2019 |
| 9:12 | 36.9° | 75.0% | 1.2500 |
| 10:12 | 39.8° | 83.3% | 1.3017 |
| 12:12 | 45.0° | 100.0% | 1.4142 |

### Why it matters

- Steeper roofs have more surface area for the same footprint, so they cost more to cover.
- Low-slope roofs below about 2:12 or 4:12 may need special membranes; shingle makers state a minimum pitch, so check the product.
- Steep roofs are harder and more dangerous to work on.

With the true area in hand, use the [roofing calculator](../roofing-calculator/) for bundles of shingles, and the [square footage calculator](../square-footage-calculator/) to measure the footprint.

## Frequently asked questions

### How do you calculate roof pitch?

Measure how many inches the roof rises over 12 inches of horizontal run. If it rises 6 inches, the pitch is 6:12.

### What is a 6/12 roof pitch in degrees?

About 26.57 degrees, a 50% slope.

### What is the roof pitch multiplier?

The factor that converts footprint to roof area: √(rise² + 144) ÷ 12. For 6:12 it is 1.118.

### What is a normal roof pitch?

Residential roofs commonly fall between about 4:12 and 9:12.

### How many squares is my roof?

Divide the true roof area by 100 square feet. A 1,677 sq ft roof is 16.8 squares.

## Sources and further reading

- [Roof slope multiplier](https://www.nachi.org/roof-slope-estimate-multiplier.htm) — InterNACHI