Roof Height Calculator
Reviewed by the My Roof Pitch editorial team · Updated · Free, no sign-up, works offline after first load
Roof rise equals half the span divided by 12, multiplied by the pitch. A 30 ft span, 8:12 pitch and 9 ft wall height gives a rise of 10 ft, so the ridge sits about 19 ft above the ground at a 33.7° roof angle.
Key takeaways
- Rise = (pitch ÷ 12) × run, where run is half the span for a symmetric gable.
- Ridge height = wall height + rise.
- A 12:12 pitch always produces a 45° roof angle regardless of span.
- Check local maximum height limits before committing to a steep pitch on a wide span.
Your measurements
Enter the values you know — results update live.
Total width of the building at the eaves, from outer wall to outer wall.
Rise per 12 inches of run.
Height of the exterior wall from ground or foundation to the top plate.
Analysis
Live results from your measurements.
Show the working
- Run:
30 ÷ 2= 15 ft - Rise:
(8 ÷ 12) × 15= 10 ft - Ridge height:
9 + 10= 19 ft - Roof angle:
atan(8 ÷ 12)= 33.69°
What this calculator does
Roof height, often called the rise, is the vertical distance from the top plate of the walls up to the ridge of a gable or hip roof. It is determined entirely by the pitch and the horizontal run — half the building span for a symmetric gable roof. Builders need this number for truss ordering, attic headroom planning, permit height checks and estimating the total ridge height above grade when stacking it on top of the wall height and foundation height.
How to use it
- Measure the building span — total width at the eaves, outside wall to outside wall.
- Divide the span by two to get the run for a symmetric gable roof.
- Enter the roof pitch as rise per 12 inches of run.
- Multiply the pitch ratio by the run to get the rise.
- Add the rise to the wall height to get ridge height above the top of the foundation or ground, as applicable.
- Check the result against any local maximum building height restrictions.
The formula
Roof rise
rise = (pitch / 12) × run, where run = span / 2 for a symmetric gable
The rise-over-run ratio applied to half the building span.
Ridge height
ridge height = wall height + rise
Total height from the ground (or whatever reference the wall height uses) up to the ridge.
Worked example
30 ft span, 8:12 pitch, 9 ft wall height.
- Run: 30 ÷ 2 = 15 ft
- Rise: (8 ÷ 12) × 15 = 10 ft
- Ridge height: 9 + 10 = 19 ft
- Angle: atan(8 ÷ 12) = 33.69°
An 8:12 roof over a 30 ft span with 9 ft walls puts the ridge about 19 ft above the ground at a 33.7° angle.
Rise by pitch for a 30 ft span (15 ft run)
| Pitch | Rise | Angle |
|---|---|---|
| 4:12 | 5.0 ft | 18.43° |
| 6:12 | 7.5 ft | 26.57° |
| 8:12 | 10.0 ft | 33.69° |
| 10:12 | 12.5 ft | 39.81° |
| 12:12 | 15.0 ft | 45.00° |
Common mistakes
- Using the full span instead of half the span (run) when the roof is a symmetric gable.
- Forgetting to add wall height, reporting only the rise as if it were total building height.
- Not accounting for the ridge board thickness or truss heel height, which add a small amount to real ridge height.
- Mixing up span (eave to eave) with run (eave to centerline).
- Ignoring local maximum height limits when planning a steep pitch on a wide span.
Assumptions and limits
- The roof is a symmetric gable, so run equals half the span.
- Wall height is measured from the reference point you want ridge height measured from.
- Ridge height excludes ridge board thickness and truss heel height.
- Pitch is constant across the full run with no breaks or dormers.
Frequently asked questions
How do I calculate roof height from pitch?
Multiply the pitch ratio (rise ÷ 12) by the run, which is half the building span for a standard symmetric gable roof.
What is the difference between span and run?
Span is the full building width from eave to eave; run is half the span, measured from the eave to the centerline of a gable roof.
How tall will my ridge be above the ground?
Add the roof rise to the wall height (and foundation height if measuring from grade) to get total ridge height.
Does a steeper pitch mean a taller roof?
Yes, for the same span, a steeper pitch increases the rise and therefore the ridge height proportionally.
What pitch gives a 45 degree roof angle?
A 12:12 pitch produces exactly a 45 degree roof angle.
How does wall height affect total building height?
Total building height is wall height plus roof rise, so taller walls with the same pitch produce a taller overall structure.
Is roof height the same as rafter length?
No. Roof height (rise) is the vertical distance to the ridge; rafter length is the sloped hypotenuse distance from the wall to the ridge.
Why do permits care about ridge height?
Many zoning codes cap maximum building height measured to the ridge, so checking this before framing avoids a costly redesign.
Related guides
Last updated 2026-10-08. Results are estimates for planning and are not a substitute for a licensed engineer or local code review.