Pitch, area, rafter length & material estimates — free and instant
Hip assumes equal pitch on all sides (common rectangular plan). For complex roofs calculate planes separately.
Enter the horizontal run (half the building width for a simple gable) and either rise or pitch.
Common rafter is the length from the ridge to the wall plate (excluding overhang). Add ridge board thickness and birdsmouth cuts on site as required.
Interested in a Pro version (save multiple roofs, PDF export, hip/valley rafters, cost estimates)?
We’ll only use your email to notify you if a Pro version launches.Roof pitch is the steepness of a roof, traditionally expressed as rise over run (e.g. 6/12 means 6 inches of vertical rise for every 12 inches of horizontal run).
Gable vs Hip: For equal-pitch rectangular buildings the same area multiplier is commonly used for both gable and simple hip roofs as a practical estimate. Complex hips, valleys and dormers need plane-by-plane calculation or professional measurement.
You can measure pitch safely from inside the loft in most cases. You only need a spirit level and a tape measure.
If the roof has multiple pitches (hips, dormers, different slopes), measure each main plane separately. Always prioritise safety — never work on a wet, steep or fragile roof without proper equipment and experience.
Once you have the rise and run, enter them in the calculator above to get the angle, area multiplier, surface area and material estimates.
| Pitch | Angle | Multiplier | Typical Use |
|---|---|---|---|
| 2/12 | 9.5° | 1.014 | Low-slope / metal |
| 3/12 | 14.0° | 1.031 | Minimum for many shingles |
| 4/12 | 18.4° | 1.054 | Common residential |
| 5/12 | 22.6° | 1.083 | Common residential |
| 6/12 | 26.6° | 1.118 | Most common residential |
| 7/12 | 30.3° | 1.158 | Steeper residential |
| 8/12 | 33.7° | 1.202 | Steeper residential |
| 9/12 | 36.9° | 1.250 | Steep |
| 10/12 | 39.8° | 1.302 | Steep / snow areas |
| 12/12 | 45.0° | 1.414 | Very steep / A-frame |
From the attic or with a level and tape measure: place a level horizontally, measure 12 inches along the level, then measure the vertical distance from the end of the level down to the roof surface. That vertical distance is the rise for a 12-inch run.
Because the roof is sloped. The steeper the pitch, the longer the rafter and the more surface area that must be covered. Always use the pitch multiplier when ordering materials.
Most asphalt shingles are sold three bundles per square (100 sq ft). Calculate roofing squares (roof area ÷ 100), then multiply by 3 and add your waste factor (usually 10–15%). Complex roofs with hips and valleys need more waste.
No. For simplicity it applies the standard pitch multiplier to the overall plan area (including overhang). This is a practical estimate for equal-pitch rectangular hip roofs. For precise take-offs on complex hips or valleys, calculate each plane or use professional measurement.
Common rafter length is from the ridge to the outside of the wall plate. The “with overhang” figure adds the sloping length of the projection beyond the wall. On site you still need to account for ridge board thickness and birdsmouth cuts.
It gives a solid planning estimate. For final material orders, especially on complex roofs (hips, valleys, dormers, multiple pitches), a professional measurement or satellite report is recommended. Always add an appropriate waste factor.
What is a roofing square?
One square equals 100 square feet of roof surface. Divide surface area by 100, then add waste for ridges, hips and cuts.
Can I use metric measurements?
Yes. Keep rise and run in the same units. The pitch ratio and multiplier work the same way whether you use inches or centimetres.
Does a steeper pitch always need more material?
For the same building footprint, yes—the surface area grows with the multiplier. Labour and safety requirements also tend to increase on steeper roofs.
Is this a substitute for a structural engineer?
No. These tools estimate geometry and material quantities for planning. Structural capacity, wind, snow loads and building regulations require qualified professionals.
For deeper reading, see our roof pitch guides on measuring pitch, reading charts, and gable vs hip area estimates.
Roof Pitch Tools is a free suite of calculators designed to be fast, accurate and easy to use on any device. All calculations run entirely in your browser — nothing is uploaded or stored. Intended for homeowners, DIY enthusiasts and contractors who need quick, reliable estimates.
Step-by-step articles to use with the calculators: