How To Calculate Truss Height

Use this interactive calculator to estimate truss rise, total truss height, and roof slope geometry from building span and roof pitch. It is ideal for quick planning of a standard symmetrical gable truss before you verify the final design with local code requirements and a qualified engineer or truss manufacturer.

Truss Height Calculator

Enter the building span, roof pitch, and optional heel height. The calculator returns the roof run, rise, and total peak height.

This calculator is for estimating geometry only. Final truss design depends on loading, spacing, lumber species, plate design, local code, wind uplift, and snow load.

Expert Guide: How to Calculate Truss Height Correctly

When people ask how to calculate truss height, they are usually trying to answer one of three practical questions. First, they may need to know how tall the roof peak will be so they can plan wall height, attic space, and overall building appearance. Second, they may be estimating material needs or comparing roof profiles before ordering manufactured trusses. Third, they may be checking whether a selected roof pitch works with local climate demands such as snow, rain drainage, and wind exposure. In every case, truss height begins with geometry, but final design always requires structural verification.

For a standard symmetrical gable truss, the most common formula is simple. Divide the total building span by two to get the run. Then multiply the run by the pitch rise and divide by the pitch run basis. In standard residential notation, pitch is typically written as something like 4/12, 6/12, 8/12, or 10/12. A 6/12 roof rises 6 units vertically for every 12 units horizontally. If your building span is 24 feet, the run is 12 feet. The rise is 12 x 6 / 12 = 6 feet. If the heel height is zero, the truss height from bearing to ridge is 6 feet. If you have a 10 inch heel, you would add that vertical dimension to the rise to get the total peak height above the bearing point.

Core formula for a symmetrical gable truss:
Truss rise = (Span / 2) x (Pitch rise / Pitch run)
Total truss height = Truss rise + Heel height

Understanding the Terms: Span, Run, Rise, and Heel Height

Accurate calculation depends on using the right terms. Span is the total width covered by the truss, usually measured from the outside of one bearing wall to the outside of the opposite bearing wall when discussing overall building width. Run is the horizontal distance from one bearing point to the centerline of the roof for a symmetrical gable truss. Rise is the vertical distance from the top of the bearing point to the apex, not including any additional heel height unless you intentionally add it. Heel height is the vertical depth at the eave where the top chord and bottom chord meet over the support. In many practical construction conversations, people use the phrase truss height to mean the rise only, while others mean the rise plus heel. That is why it is important to define the reference point before placing an order or drafting a section detail.

For a single slope shed truss, the process changes slightly because the run is typically the full span rather than half the span. If a shed roof spans 16 feet and the pitch is 3/12, the rise is 16 x 3 / 12 = 4 feet. If the low end starts with a heel height of 8 inches, the high end total height above the low bearing line is 4 feet 8 inches. This is why calculators should clearly distinguish between symmetrical and single slope shapes.

Step by Step Process for Calculating Truss Height

1. Measure the span. Confirm the exact width the truss must cover.
2. Identify the roof style. Decide whether you have a symmetrical gable truss or a single slope shed truss.
3. Convert pitch into a ratio. Example: 6/12 means 6 inches of rise for every 12 inches of horizontal run.
4. Determine the run. Use half the span for a symmetrical gable. Use the full span for a shed truss.
5. Calculate rise. Multiply run by rise/run pitch ratio.
6. Add heel height if needed. This gives total peak height above the bearing point.
7. Check roof angle if useful. The angle is arctangent of rise divided by run.

Using this sequence avoids the most common mistakes. The biggest errors happen when someone uses the full span instead of half-span for a gable truss, or forgets to include the heel height when estimating overall section height. Another common issue is mixing inches and feet. If the pitch is expressed as 6/12 and the run is in feet, you can still use the same ratio because the units cancel out, but you must keep all dimensions consistent when adding heel height. For example, 10 inches must be converted to 0.833 feet if the rest of your math is in feet.

Pitch Conversion Table for Common Roof Profiles

The following comparison table shows common roof pitches, approximate roof angles, and the rise for a 24 foot span gable truss. Since the run is half the span, the run used here is 12 feet. These are real geometric values and are very useful during concept design.

Roof Pitch	Slope Ratio	Approx. Angle	Rise over 12 ft Run	Total Height with 12 in Heel
3/12	0.25	14.0 degrees	3.0 ft	4.0 ft
4/12	0.333	18.4 degrees	4.0 ft	5.0 ft
6/12	0.50	26.6 degrees	6.0 ft	7.0 ft
8/12	0.667	33.7 degrees	8.0 ft	9.0 ft
10/12	0.833	39.8 degrees	10.0 ft	11.0 ft
12/12	1.00	45.0 degrees	12.0 ft	13.0 ft

Why Truss Height Matters Beyond Basic Geometry

Truss height affects far more than roof appearance. A taller truss often creates more interior volume, which can be useful for vaulted ceilings, attic storage, or mechanical routing. However, greater height can also increase material use, shipping constraints, and crane considerations. In snow regions, slope selection may affect snow shedding behavior, though structural design must still be based on local code loads. In wind-prone regions, overall roof profile can influence uplift and lateral pressures. This is why truss height should never be chosen by appearance alone.

Building science also plays a role. Higher heel heights are often used to improve insulation continuity at the eaves. In modern energy-conscious construction, raised heel trusses can preserve the full depth of attic insulation over the exterior wall line. That means the final truss height may be noticeably larger than the simple geometric rise from pitch alone. If you are trying to estimate fascia elevation, ridge height, or attic clearances, the heel dimension deserves special attention.

Comparison Table: Example Truss Heights by Span and Pitch

This second table compares estimated truss rise for several common spans using a standard gable truss with zero heel height. It illustrates how quickly peak height grows as pitch increases.

Span	4/12 Pitch Rise	6/12 Pitch Rise	8/12 Pitch Rise	12/12 Pitch Rise
20 ft	3.33 ft	5.00 ft	6.67 ft	10.00 ft
24 ft	4.00 ft	6.00 ft	8.00 ft	12.00 ft
30 ft	5.00 ft	7.50 ft	10.00 ft	15.00 ft
36 ft	6.00 ft	9.00 ft	12.00 ft	18.00 ft

Common Mistakes When Calculating Truss Height

• Using full span for a gable truss. For symmetrical roofs, the run is half the span.
• Ignoring heel height. This can lead to underestimating total section height and exterior elevations.
• Mixing units. Inches, feet, and meters must be handled consistently.
• Confusing roof pitch with roof angle. A 6/12 pitch is not a 6 degree roof.
• Assuming geometry equals structural approval. Truss plates, web layout, spacing, and loading still control the real engineered design.

How Roof Angle Relates to Truss Height

Sometimes homeowners and designers think in degrees instead of pitch. The relationship is simple: angle = arctangent of rise divided by run. A 6/12 roof has a ratio of 0.5, so the angle is approximately 26.6 degrees. This is useful when coordinating with architectural software or local ordinances that reference slope in degrees. Still, most truss suppliers in North America prefer pitch notation because it translates directly to framing dimensions.

Once you know the angle, you can also estimate top chord length with the Pythagorean theorem. For a 24 foot span gable roof at 6/12 pitch, the half-span run is 12 feet and the rise is 6 feet. The sloped top chord from bearing to ridge is the square root of 12 squared plus 6 squared, which is about 13.42 feet before accounting for overhang and seat cut details. While this is not always needed for a basic truss height calculation, it helps when visualizing actual roof geometry.

Real World Design Considerations That Change the Final Number

Manufactured trusses are engineered components, not just triangles. The final shop drawing may include raised heels, dropped top chords, different bearing assumptions, cantilevers, or energy details that change the section profile. Loads are equally important. Roof dead load includes sheathing, underlayment, roofing material, ceiling finish if supported, and mechanical items. Roof live load, snow load, and wind load vary by location and code edition. If you are building in a snow-prone area, a pitch that looks reasonable on paper may still need a stronger or deeper truss to satisfy design requirements.

For authoritative background on structural loads and roof design context, review the FEMA structural loads guidance at fema.gov. For wood construction fundamentals and material behavior, the U.S. Forest Products Laboratory Wood Handbook is a valuable reference at fpl.fs.usda.gov. For practical roof framing geometry and educational discussion, Oregon State University Extension provides helpful framing resources at oregonstate.edu.

When to Use a Calculator and When to Call an Engineer

A calculator is excellent for planning, visualization, and budget-stage estimating. It is perfect when you want to compare how a 4/12 roof looks against a 6/12 roof, or how much additional peak height results from a raised heel. It is also useful for checking ridge elevation against zoning height limits, attic volume, and siding or stair conflicts. However, you should call an engineer, architect, or licensed truss designer when any of the following apply:

• The span is large or the building use is unusual.
• You are in a high snow, high wind, or seismic area.
• You need a vaulted ceiling, attic truss, scissor truss, or bonus room truss.
• The roof includes offsets, valleys, piggyback sections, or large overhangs.
• Local permitting requires stamped truss calculations or sealed structural documents.

Quick Example Calculations

Example 1, 24 foot span, 6/12 pitch, no heel: run = 24 / 2 = 12 feet. Rise = 12 x 6 / 12 = 6 feet. Total truss height = 6 feet.

Example 2, 30 foot span, 8/12 pitch, 1 foot heel: run = 30 / 2 = 15 feet. Rise = 15 x 8 / 12 = 10 feet. Total truss height = 10 + 1 = 11 feet.

Example 3, shed truss, 16 foot span, 3/12 pitch, 8 inch heel: run = 16 feet. Rise = 16 x 3 / 12 = 4 feet. Heel = 0.667 feet. Total height difference = 4.667 feet.

Final Takeaway

If you want to know how to calculate truss height, remember this simple rule: identify the correct run, apply the roof pitch ratio, and add heel height if it is part of the design. For a standard gable truss, the run is half the building span. For a shed truss, it is usually the full span. That one distinction solves many framing misunderstandings. Once you have the basic geometry, compare the result against architectural needs, insulation strategy, and local loading conditions. The calculator above gives you a fast and practical estimate, but the final truss order should always follow engineered drawings and local code review.

Educational use only. Always confirm dimensions, bearing conditions, and required structural loads with your local building department and truss supplier before construction.