Roof Height Calculator
Daniel Brooks is a civil engineer with 10 years of experience and the founder of RoofPitchCalculator.org. He develops the site's calculators and technical guides around transparent formulas, geometry and clearly stated assumptions.
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Roof height depends on the horizontal run and the roof slope. For a centred gable roof, the run is half the full building span. Multiply that run by the rise-to-run ratio to get the roof rise, then add any reference or eave height if you need the ridge or peak height from a lower datum. This roof height calculator performs those steps automatically and also works backwards from a height limit.
How to Use the Roof Height Calculator
This calculator is designed for several common roof-height questions rather than forcing every user into one input method. Choose the option that matches the measurements you already know.
- Choose a calculation method. Use Building Span + Slope, Run + Slope, Rafter + Run, Height Limit or Mean Roof Height.
- Select the roof layout. Gable and simple hip roofs normally use half the full span as the run. A shed or lean-to roof uses the full horizontal span. Flat mode has zero geometric roof rise.
- Enter your dimensions. Use US/Imperial or Metric units. The calculator converts the dimensions internally before applying the geometry.
- Enter the roof slope where required. You can use x:12 pitch, degrees or slope percentage.
- Read the roof rise and peak height. The results also show run, rafter line length, roof angle, equivalent pitch, slope percentage and a mean roof-height reference.
If you do not know the slope yet, calculate it first with our Roof Pitch Calculator. If you need a quick pitch-to-angle conversion, use the Roof Pitch Chart.
Roof Height Formula
The basic calculation is right-triangle geometry. The horizontal run is one side of the triangle, the roof rise is the vertical side and the rafter line is the hypotenuse.
If you enter a reference height, such as the height from your chosen datum to the roof run line:
When the slope is entered as an angle:
When the slope is entered as a percentage:
These formulas are the basis of the roof height calculator with pitch, roof pitch height calculator, roof height pitch calculator and roof slope height calculator workflows on this page.
Roof Rise vs Ridge Height vs Peak Height
These terms are often mixed together, but they are not always the same measurement.
The vertical distance from the horizontal roof run line up to the ridge or peak. This is the pure right-triangle result.
The height of the ridge from whatever datum you are using. For a pitched roof, this normally equals the reference height plus roof rise.
The vertical height to the highest roof point. On a simple gable roof, the ridge is also the peak.
A separate reference used in some code and wind-design contexts. It should not be confused with ridge height.
So if you searched for a roof peak height calculator or roof ridge height calculator, the most important detail is the reference point from which you want the height measured.
Gable Roof Height Calculator
For a centred symmetrical gable roof, the ridge sits over the midpoint of the building span. The horizontal run for one side is therefore:
The gable roof height calculator then applies the chosen roof pitch, angle or slope percentage to that half-span.
Worked Example: 28 ft Span, 8:12 Pitch and 9 ft Reference Height
Suppose a centred gable roof spans 28 ft and has an 8:12 pitch. The horizontal roof run is half the span:
That is approximately 18 ft 4 in from the same reference datum. The roof angle is about 33.69°.
Hip Roof Height Calculator
For a simple centred rectangular hip roof, the vertical roof height is still determined by the horizontal run in the slope direction and the roof pitch. If you enter the full span across that slope direction, the calculator uses half the span to the ridge or peak reference.
This makes the tool useful as a hip roof height calculator for simple uniform-pitch geometry. More complicated hip roofs may have different spans, ridge lengths or intersecting roof sections, so make sure the span you enter corresponds to the cross-section whose height you are calculating.
Shed and Lean-To Roof Height
A shed or lean-to roof uses a different run convention from a centred gable. The single roof plane extends across the full horizontal span, so the full span is the run.
Roof Height From Run and Pitch
If you already know the horizontal run, use the Run + Slope method. This avoids converting the run back into a full building span.
For example, a 10 ft run at 30° gives:
This mode is particularly useful when working from drawings or an existing roof where the ridge is not necessarily centred.
Roof Height From Rafter Length and Run
The Rafter + Run mode works backwards from the right triangle. If the rafter line length and horizontal run are known, roof rise is:
The rafter value must represent the same geometric triangle as the run. Do not include an eave overhang if the run stops at the wall or bearing reference. For a more detailed framing calculation, including optional overhang and ridge-board geometry, use the Rafter Length Calculator.
Roof Height Limit and Maximum Roof Pitch
The Height Limit mode reverses the normal calculation. Instead of asking how high a known pitch will rise, it asks how much rise is available below a maximum peak or ridge height.
For example, if the maximum allowed geometric peak is 15 ft, the reference height is 9 ft and a centred gable has a 24 ft span, the available rise is 6 ft and the run is 12 ft. That corresponds to a 6:12 pitch.
Mean Roof Height Calculator
The mean roof height calculator mode is intentionally separate from the normal ridge-height calculation because mean roof height is a defined reference used in some building-code and wind-design provisions.
The simple arithmetic average is:
The calculator also shows an IRC-style mean roof height reference. The 2024 International Residential Code includes provisions where mean roof height is the average of roof eave height and the highest roof point, while for roof slopes of 10° or less the eave height is permitted to be used instead.
That distinction is why an average roof height calculator and a code-specific mean roof height reference are not always exactly the same thing.
Roof Height by Common Pitch
For a centred 24 ft gable roof, the run is 12 ft. Because an x:12 pitch means x units of rise for every 12 units of run, the roof rise over that 12 ft run is numerically the same as the pitch rise.
| Roof pitch | Roof angle | Run for 24 ft centred gable | Roof rise | Peak height with 9 ft reference |
|---|---|---|---|---|
| 2:12 | 9.46° | 12 ft | 2 ft | 11 ft |
| 3:12 | 14.04° | 12 ft | 3 ft | 12 ft |
| 4:12 | 18.43° | 12 ft | 4 ft | 13 ft |
| 5:12 | 22.62° | 12 ft | 5 ft | 14 ft |
| 6:12 | 26.57° | 12 ft | 6 ft | 15 ft |
| 8:12 | 33.69° | 12 ft | 8 ft | 17 ft |
| 10:12 | 39.81° | 12 ft | 10 ft | 19 ft |
| 12:12 | 45.00° | 12 ft | 12 ft | 21 ft |
This table is pure right-triangle geometry. It does not include framing heel height, ridge thickness, sheathing, roof covering or another construction build-up.
Roof Truss Height Calculator: What This Tool Can and Cannot Tell You
Users searching for a roof truss height calculator often need the geometric rise from the bearing/run line to the truss peak. For a simple symmetrical truss profile, the same span-and-pitch geometry can provide that rise.
However, a finished truss dimension is not determined by pitch and span alone. Actual truss geometry can depend on bearing location, bottom-chord position, top-chord depth, raised heels, energy heels and the engineered truss design.
A roof truss heel height calculator is therefore a different problem. This calculator does not design or determine heel height, truss member sizes, loads, connector plates or structural adequacy.
Why the Finished Roof May Be Higher Than the Geometric Result
The calculated rise is based on an ideal geometric line. A completed building can end up slightly different depending on exactly where the measurements are taken.
- truss heel height or rafter bearing geometry;
- ridge board or structural ridge-beam arrangement;
- rafter or top-chord depth;
- roof sheathing;
- underlayment and roof covering;
- battens, counter-battens or other build-up;
- the grade, wall or datum used to define the starting height.
This is why the main result should be treated as geometric roof height unless your reference dimensions were specifically chosen to match the finished surfaces you need.
Measuring the Inputs Correctly
Good inputs matter more than extra decimal places. Before calculating, identify which horizontal and vertical references you are actually measuring.
For a centred gable, measure the full horizontal span across the roof-slope direction. The calculator divides it by two to get one run.
Measure horizontally, not along the roof surface. Run and rafter length are different dimensions.
Use one clearly defined datum for both the starting height and final peak height. Mixing different reference levels produces a misleading total height.
Confirm whether the value is x:12, degrees or percentage. The calculator accepts all three, but they are not numerically interchangeable.
If you need help understanding rise, run and pitch before measuring, see our Roofing Guides and the main Roof Pitch Calculator.
Roof Height Calculator FAQs
How do I calculate roof height?
Find the horizontal run, convert the roof pitch into a rise-to-run ratio and multiply the run by that ratio. This gives roof rise. Add your reference or eave height if you need the total ridge or peak height from that datum.
How do I calculate the height of a roof from pitch?
For x:12 pitch, multiply the horizontal run by x ÷ 12. For example, a 12 ft run at 6:12 rises 6 ft. This is the core calculation behind a height of roof calculator.
How do I calculate ridge height from building width?
For a centred gable, divide the full building span by two to get the run. Multiply that run by the slope ratio to get rise, then add the reference height if you need the ridge height from a lower datum.
Can I use this as a roof ridge height calculator?
Yes. Use Building Span + Slope for a centred roof or Run + Slope if you already know the horizontal run. Enter a reference height when you need the ridge height from ground, wall, plate or another defined datum.
Can I use this as a roof peak height calculator?
Yes. The calculator reports the peak/ridge height from the reference datum you enter. On a simple gable roof, the ridge is also the highest roof point.
What is the formula for a 6:12 roof height?
A 6:12 pitch has a slope ratio of 0.5. Multiply the horizontal run by 0.5. A 12 ft run therefore has 6 ft of rise.
Does a gable roof use half the building width?
A centred symmetrical gable uses half the full span measured across the roof-slope direction. If the ridge is off-centre, calculate each side from its actual run instead.
Does a hip roof use the same height formula?
For a simple centred uniform-pitch hip roof, the ridge or peak height is still controlled by the horizontal run in the relevant cross-section and the roof slope. Complex hip layouts should be checked using the actual geometry of the section being measured.
What is mean roof height?
In the IRC-style reference used by this calculator, mean roof height is generally the average of roof eave height and the highest roof point, while eave height is permitted to be used for roof slopes of 10° or less. Always check the definition required for your project.
Is mean roof height the same as ridge height?
No. Ridge height is the height of the ridge itself. Mean roof height is a separate reference and is normally lower than the ridge on a pitched roof.
Can I calculate roof height in metres?
Yes. Switch to Metric and enter dimensions in metres, centimetres or millimetres where available. The geometry is the same regardless of the unit system.
Can this calculate truss heel height?
No. It can calculate geometric roof or truss rise from span and pitch, but heel height is a framing and engineered-truss detail that depends on the actual truss design.
Can I calculate rafter length from the same measurements?
The Roof Height Calculator shows the geometric rafter line length as a supporting result. For dedicated rafter calculations with overhang and additional framing geometry, use the Rafter Length Calculator.
How does roof height affect roof area?
A greater rise over the same horizontal run means a steeper roof and therefore a longer sloping surface. To calculate the resulting roof surface area, use the Roof Area Calculator.
Technical Reference and Calculation Limits
The calculator uses standard right-triangle geometry for roof rise, run, angle, pitch and rafter line length. Its IRC-style mean roof height reference follows the 2024 International Residential Code wording used in roof-height provisions: the average of roof eave height and the highest roof point, with eave height permitted for roof slopes of 10° or less.
International Residential Code, 2024 — mean roof height reference
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