What this calculator does
Roof truss cost calculators built around a single "average price" go stale fast, because truss prices vary hugely with span, timber or steel construction, roof pitch and which supplier is quoting. This calculator instead starts from the same truss count used by a standard truss-spacing calculation, then applies whatever price per truss you enter, so the cost estimate stays current no matter what a supplier quotes.
The truss count follows the common Australian on-centre spacing convention, most often 600 mm, though it accepts any spacing. Multiplying that count by an editable price per truss, and adding an optional delivery and crane hire figure, gives a total that can be updated in seconds when a real quote comes in.
The formula
The truss count is the building length divided by the on-centre spacing, rounded up, plus one extra truss to cap the run. That count is then multiplied by the price entered per truss, and any delivery or crane hire cost is added on top for the total.
| Term | Meaning |
|---|---|
| On-centre spacing | The gap measured from the centre of one truss to the centre of the next, commonly 600 mm in Australian residential roofing. |
| Truss count | Building length ÷ spacing, rounded up, plus one to cover both ends of the run. |
| Price per truss | The cost of a single truss, which varies by span, pitch and material. Always enter this fresh rather than relying on a fixed figure. |
The inputs explained
| Field | What to enter |
|---|---|
| Building length (m) | The length of the building along which trusses are spaced. |
| On-centre spacing (mm) | The on-centre spacing between trusses, commonly 600 mm. |
| Price per truss ($) | The price per truss quoted by a supplier or manufacturer. This is never assumed and must be entered. |
| Delivery & crane hire (optional) ($) | Any delivery and crane hire cost on top of the trusses themselves, if known. Leave at 0 to see truss cost alone. |
When to use it
Costing a new build before ordering
Working from a supplier's price-per-truss quote and the planned building length gives a ballpark total before trusses are ordered, without relying on any published average price that may no longer be current.
Comparing supplier quotes
Two suppliers quoting different prices per truss for the same building length and spacing can be compared directly on total cost, once delivery is factored in separately for each.
Checking a builder's roofing allowance
If a build quote includes a roofing allowance, working out the truss count independently and applying a market price per truss checks whether that allowance is realistic.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How total cost scales with price per truss
A fixed 12 m building length at 600 mm on-centre spacing, across a range of prices per truss.
| Price per truss | Total estimated cost | Trusses needed | Cost per metre of building length |
|---|---|---|---|
| $100 | $2,100.00 | 21 | $175.00 |
| $150 | $3,150.00 | 21 | $262.50 |
| $200 | $4,200.00 | 21 | $350.00 |
| $250 | $5,250.00 | 21 | $437.50 |
| $300 | $6,300.00 | 21 | $525.00 |
Questions
Why does this calculator not just quote a fixed truss price?
Truss prices vary enormously by span, timber versus steel construction, roof pitch and supplier, so any single published figure would be wrong for most roofs and would go stale as material costs move. Entering the actual quoted price keeps the total accurate.
What spacing should I use?
600 mm on-centre is the most common residential spacing in Australia, but engineered trusses are sometimes spaced wider, such as 900 mm or 1200 mm, depending on the roof load and design. Check the truss design or engineering drawings for the actual spacing used.
Does this include installation labour?
No. This estimates the cost of the trusses themselves plus any delivery and crane hire entered. Installation labour, bracing, tie-downs and roof covering are separate costs not included here.
How is the truss count worked out?
The same way as the roof truss count calculator: building length divided by on-centre spacing, rounded up, plus one truss to cap the run. This calculator simply carries that count through to a cost.
For the truss count on its own, without a cost attached, see the roof truss count calculator. For a fence-building project on the same site, the picket spacing calculator works out picket layout the same way.