Free Online Tool · Rise Over Run
Roof Pitch Calculator — Instantly Find Pitch, Angle & Slope
Enter the rise and run of your roof and get the pitch ratio, the angle in degrees, the slope percentage and the roof pitch multiplier in real time — everything you need for planning, measuring and ordering material.
Roof Pitch Calculator
LIVE RESULTStandard run = 12 in
Conventional / standard slope
Tip: the calculator updates as you type. Switch between imperial and metric units with the toggle above.
How to Use This Roof Pitch Calculator
The tool turns two simple measurements into every figure a roofer, builder or DIY homeowner needs. Follow these three steps.
Step 1: Enter Rise and Run
Type the vertical rise into the first box and the horizontal run into the second. Run is traditionally measured over a 12-inch span, so a roof that climbs 6 inches across that span is a 6:12 pitch.
Step 2: Choose Your Output
The results panel shows the pitch as a ratio, the angle in degrees, the slope as a percentage and the roof pitch multiplier all at once, so you do not need a separate roof pitch angle calculator.
Step 3: Read Your Results
Add your building footprint area to estimate the finished roof surface area for ordering shingles, felt or metal sheeting.
What Is Roof Pitch?
Roof pitch is the measure of how steep a roof is. It is one of the most important numbers in any roofing project because it affects drainage, the material you can use, the cost and even the look of the building.
Roof Pitch Defined: Rise Over Run Explained
Pitch is most commonly written as rise over run — the vertical height the roof gains for a given horizontal distance. A 6:12 roof rises 6 inches for every 12 inches travelled horizontally. This ratio is the foundation of every calculation on this page.
Pitch vs. Slope — What's the Difference?
Traditional Definition: Rise Over Span
In traditional usage, pitch meant rise divided by the full span of the building, while slope meant rise divided by run (half the span).
Modern Usage: Why the Terms Are Used Interchangeably
Today most builders, calculators and manufacturers treat pitch and slope as the same thing and base both on rise over run. This calculator follows that modern, rise-over-run convention.
How to Calculate Roof Pitch
If you want to know how to calculate roof pitch by hand, here are the formulas the calculator uses.
The Basic Pitch Formula (Rise ÷ Run)
How to Calculate Roof Pitch in Degrees
Using the Arctangent Function
Worked Example: Converting a 4:12 Pitch to 18.43°
For a 4:12 roof, arctan(4 ÷ 12) = 18.43°. A 6:12 roof works out at 26.57°, and a 12:12 roof at exactly 45°.
How to Calculate Roof Pitch as a Percentage
The Roof Pitch Multiplier Formula
Why the Multiplier Matters for Material Estimates
Multiply your flat (plan) area by the roof pitch multiplier to get the true sloped surface area. A 1,500 ft² footprint with a 6:12 pitch needs about 1,677 ft² of roofing material.
How to Measure Roof Pitch On-Site
Tools You'll Need
A spirit level at least 12 inches long and a tape measure. A speed square also works well.
Measuring Pitch from Inside the Attic
- Hold one end of the level against the underside of a rafter.
- Level it, then measure 12 inches along it from the rafter contact point.
- At that 12-inch mark, measure straight down to the rafter — that distance is your rise.
- Record the result as X:12.
Measuring Pitch on the Roof Surface
The same method works on top of the roof: rest the level on the surface, level it, and measure the rise at the 12-inch mark. Always follow safe working-at-height practice.
Roof Pitch Chart & Conversion Table
Pitch-to-Angle Reference Table
| Pitch (X:12) | Angle | Slope % | Multiplier |
|---|---|---|---|
| 0:12 | 0.00° | 0% | 1.0000 |
| 1:12 | 4.76° | 8.3% | 1.0035 |
| 3:12 | 14.04° | 25% | 1.0308 |
| 4:12 | 18.43° | 33.3% | 1.0541 |
| 6:12 | 26.57° | 50% | 1.1180 |
| 9:12 | 36.87° | 75% | 1.2500 |
| 12:12 | 45.00° | 100% | 1.4142 |
How to Estimate Roof Material from Footprint Area
Take the plan area of the building, multiply by the multiplier for your pitch from the table above, then add an allowance for waste, overhangs and ridges.
Roof Pitch by Roof Type & Scenario
Low-Slope and 5-Degree Roof Pitch Requirements
A 5 degree roof pitch rises about 9 mm per 100 mm of run, or roughly 87 mm per metre. It is common for rooflights and low-pitch systems but needs membranes or sheets rated for low slopes.
Minimum Pitch for Lean-To / Mono-Pitch Roofs
A lean-to or mono-pitch roof should generally have a minimum fall of about 1/4 inch per foot, adjusted for the local code and the chosen covering.
Standard Pitch Ranges for Common Roof Materials
Asphalt Shingles
Usually 4:12 and above; special underlayment is needed from 2:12 to 4:12.
Metal Panels
Standing-seam metal can go as low as 1:12 to 3:12 depending on the profile.
Clay & Concrete Tile
Typically wants a steeper pitch, often 4:12 or more for reliable weather resistance.
Frequently Asked Questions
What is a good roof pitch?
Most residential roofs sit between 4:12 and 9:12. That range drains water and snow well while staying practical to build and walk on.
What is the minimum roof pitch for shingles?
Asphalt shingles are generally rated to a minimum of 2:12, but most manufacturers require special low-slope underlayment below 4:12. Always check the product specification and your local building code.
Is roof pitch the same as roof angle?
They describe the same slope in different units. Pitch is a ratio such as 6:12; the angle is that ratio converted to degrees with the arctangent function.
How do I convert 5 degrees to a roof pitch?
A 5 degree pitch rises roughly 9 mm per 100 mm of run (about 87 mm per metre), which is close to a 1:11.4 ratio.