Your truss, drawn to scale
Fink web
Need a roofing contractor for this project?
Take the span, pitch and truss count you just worked out to a roofing pro. They handle the installation, the replacement or the repair, and can price the finished roof rather than just the frame.
- Roof installation
- Roof replacement
- Roof repair
Planning estimates only. Always confirm against a sealed engineered truss design before ordering or building.
- Calculators
- 17 Calculators
- Truss shapes
- 11 Truss shapes
- Data stored
- 0 Data stored
- Forever
- Free Forever
The basics
What is a Shed Truss?
A shed truss is the one truss most people can genuinely build themselves, and the economics back that up at small spans.
A short shed truss costs noticeably less in lumber than a delivered equivalent, and across the eleven trusses a 20 ft shed needs that adds up to real money if you have a flat surface and a spare weekend.
The saving shrinks as span grows. At 24 ft you are at the edge of what site-building should attempt, and a plant-made truss will be lighter and stiffer than anything gusseted by hand (opens in a new tab).
- Light enough to hand-set A 12 to 16 ft shed truss weighs roughly 45 to 80 lb, so two people can walk it up a wall without machinery.
- Simple joints Half-inch plywood gussets on both faces, glued and nailed, do the job at these spans.
- Standard spacing works 24 in on centre matches sheathing exactly. Tighter spacing is rarely worth the extra trusses on a shed.
- Permits are often simpler Many jurisdictions exempt small detached accessory buildings from structural review, though the threshold varies. Check locally rather than assuming.
Cut the overhang tails last
Leave the top chords long, install the trusses, then snap one chalk line across all the tails and cut them in place. You get a straight fascia even if a truss or two sits slightly off.
The maths
Shed Truss Formula
Shed truss geometry
The heel cut is the pitch angle itself and the peak cut is its complement, so the two always add to 90 degrees.
Method
How to Calculate a Shed Truss
A shed truss is a small-span gable, so the maths is one triangle: halve the span, apply the pitch, and take the hypotenuse.
- 1 Measure the span Outside face of one wall plate to the outside face of the other. A nominal 12 ft shed usually spans 11 ft 9 in, so measure rather than assume.
- 2 Choose a pitch 4:12 is the sweet spot for sheds. Enough slope for shingles, low enough that the truss stays light and the shed does not look top-heavy.
- 3 Set the overhang 6 to 12 in keeps rain off the walls. Past 16 in on a shed the tail starts catching wind and needs its own support.
- 4 Cut, gusset, repeat Build the first truss on a flat surface, check it against the drawing, then use it as the template for the rest.
The trick that makes site-built trusses accurate is the jig. Snap the bottom chord line on a garage floor, screw down blocks at the heel and peak positions the calculator gives you, and build every truss inside those blocks.
They will come out identical, which matters far more than any single truss being perfect. A roof plane made of identical trusses is flat even when the shape is a fraction off.
Worked example
A 12 ft shed at 4:12 has a 6 ft run and a 6 ft 4 in top chord, with a 12 in overhang adding another 12⅝ in of tail. At 24 in centres a 20 ft long shed needs 11 trusses. Check the result against your local requirements before cutting.
Top chord length from the heel to the peak, excluding overhang. Add the tail figure the calculator reports.
| Span | 3:12 | 4:12 | 6:12 | 8:12 |
|---|---|---|---|---|
| 8 ft | 4' 2" | 4' 3" | 4' 6" | 4' 10" |
| 10 ft | 5' 2" | 5' 3" | 5' 7" | 6' 0" |
| 12 ft | 6' 2" | 6' 4" | 6' 9" | 7' 3" |
| 16 ft | 8' 3" | 8' 5" | 8' 11" | 9' 8" |
| 20 ft | 10' 4" | 10' 7" | 11' 2" | 12' 0" |
| 24 ft | 12' 5" | 12' 8" | 13' 5" | 14' 5" |
Note: Cut angles: 3:12 is 14.0 degrees, 4:12 is 18.4, 6:12 is 26.6 and 8:12 is 33.7, measured from horizontal.
The tool
Why Choose Our Shed Truss Calculator
Built around the spans people actually build sheds at, and around the fact that you will probably be cutting these yourself.
- Sized for 8 to 24 ft The range where site-building genuinely makes sense, rather than a generic tool stretched down to shed size.
- Overhang tail worked out The sloping tail is longer than the horizontal overhang you specify, and the tool reports both.
- Truss count and layout Enter the shed length and get the exact number, including the frame at each end.
- Print it for the jig The results page is print-styled, so you can take the chord lengths and cut angles to the bench.
More tools
Explore Related Truss Calculators
Calculators that pair with the shed tool, each running the same geometry engine.
- Gable Roof Truss Calculator Live geometry, automatic web pattern selection and a complete material take-off. Open calculator
- Gambrel Roof Truss Calculator Two slopes, one cut list. Works for 12 ft, 16 ft, 24 ft and 40 ft gambrel spans. Open calculator
- Roof Truss Spacing Calculator Truss count, layout and sheathing check for any on-centre spacing. Open calculator
Get a free roofing quote
Roof installation, replacement and repair, quoted by a contractor who can visit the site. Bring your numbers from above and skip the guesswork on the rest of the job.
- Free quote
- No obligation
- Fast callback
Answers
Frequently Asked Questions
Common questions about shed roof truss design calculator.
How do I calculate shed truss length?
Halve the span to get the run, then multiply by the slope factor for your pitch. For 4:12 that factor is 1.054, so a 12 ft shed has a 6 ft run and a 6 ft 4 in top chord. Add the overhang tail, which at 4:12 adds about 12⅝ in for a 12 in overhang.
What pitch should a shed roof truss be?
4:12 for most sheds. It sheds water reliably, works with standard asphalt shingles, keeps the truss light and does not make an 8 ft wall look like a chapel. Go to 6:12 if you want a little loft storage, or 3:12 if headroom under a low eave matters more.
Can I build a 24 ft shed truss out of 2x4s?
With a proper web pattern, yes. A 24 ft span with 2x4 chords needs a fink or double-fink layout and good gussets, and it sits right at the edge of what site-building should attempt. At that size, quoted trusses are often the smarter call.
How much overhang should a shed truss have?
6 in is the practical minimum to keep water off the siding, 12 in is standard, and 16 in is about the maximum before the tail needs its own support. Remember the overhang is a horizontal projection, so the actual sloping tail is longer.
Do shed trusses need hurricane ties?
Almost always, and most inspectors will ask. Toe-nailing alone gives very little uplift resistance, and a shed roof is exactly the kind of light structure that lifts. One tie per truss per bearing is inexpensive insurance.
What spacing should shed trusses be?
24 in on centre is standard and matches 4 ft sheathing perfectly. Use 16 in only for heavy snow loads or if you plan to hang significant weight from the bottom chords.
References
Shed Truss Sources & Further Reading
Related calculators on this site, plus the standards and reference works the figures on this page are based on. External links open in a new tab.
Authoritative external references
- WIKI Shed, Wikipedia (opens in a new tab)
- WIKI Roof pitch, Wikipedia (opens in a new tab)
- ORG SBCA, truss handling and bracing guidance (opens in a new tab)
- STD American Wood Council, NDS and span tables (opens in a new tab)
- CODE International Code Council, model building codes (opens in a new tab)
Codes and standards are revised on their own cycles. Confirm the current edition adopted in your jurisdiction with your local building department before relying on any figure.