Roof Pitch Calculator

What is roof pitch?

Roof pitch describes how much a roof rises over a horizontal distance. This roof pitch calculator converts rise and run into pitch in inches per foot, angle in degrees, slope percentage and a rafter-length multiplier. It can help with early planning whether you searched for a pitch calculator or a rafter calculator.

Pitch is written as rise over a run of 12 inches. For example, a 6/12 pitch rises 6 inches for every 12 inches of horizontal run. The angle describes the roof's slope in degrees. The multiplier helps convert horizontal run into the length along the rafter.

Why roof pitch matters

Pitch affects the shape of a roof and can influence material choices, drainage, usable attic space and construction plans. Before choosing a design, compare the calculator's results with the requirements for your roofing materials and local conditions.

Rafter length helps you estimate lumber needs and discuss a design with a contractor. The result is a starting measurement, not a complete cut list or materials quote. Actual framing can include details the calculator does not model, such as overhangs, ridge connections and cut angles.

How to use this roof pitch calculator

1. Enter the vertical rise in inches. Use the height change from the horizontal reference to the roof surface.
2. Enter the horizontal run in inches. Measure the horizontal distance that corresponds to the rise.
3. Keep rise and run in the same units. The calculator uses their ratio, so mismatched units produce an incorrect result.
4. Review the pitch, angle, slope, multiplier and rafter length per foot of run. Use the result to compare roof designs or prepare questions for a roofing professional.

Roof pitch calculator example

How to read your roof pitch results

Pitch gives you the familiar rise-per-12-inch-run format. Angle expresses the same steepness in degrees, while slope presents rise divided by run as a percentage. These are different ways to describe the roof's geometry.

The pitch multiplier converts horizontal run to sloped rafter length. Multiply the horizontal run by that factor to estimate the length along the roof surface. The displayed rafter length per foot of run applies the multiplier to a 12-inch horizontal run. It does not include overhangs, joints or cutting allowances.

How to improve your roof planning

1. 01

   Verify the measurements

   Measure rise and horizontal run from the same roof section, and check that both entries use inches. If you are measuring an existing roof, confirm your reference points before ordering materials.

2. 02

   Compare designs before buying

   Test alternative rise and run measurements to see how pitch, angle and rafter length change. Ask a roofer or designer to confirm that the chosen pitch works with the materials and building plans.

3. 03

   Build in project details

   Use the result as a geometric estimate, then account separately for overhangs, connections, cuts and waste when preparing a materials list. Get a complete takeoff from a qualified professional before placing an order.

Common roof pitch calculator mistakes

• Mixing measurement units

  Entering rise in inches and run in another unit changes the ratio and gives a misleading result. Convert both measurements to the same unit first.

• Treating rafter length as the full cut length

  The calculator measures along the slope for the entered run. It does not add overhangs, connection details or cutting allowances.

• Confusing pitch with angle

  A 6/12 pitch and a 26.57° angle describe the same sample roof in different formats. Use the format requested by your plans or roofing professional.

The roof pitch formula

Key terms

Rise

The vertical height change from the horizontal reference to the roof surface.

Run

The horizontal distance used with the rise to describe the roof's steepness.

Pitch multiplier

The factor used to convert horizontal run into sloped rafter length.