This floor joist reference table shows the joists needed for a range of floor width (across joists) values, assuming a joist spacing of 0.4 m. Every figure is computed with the same engine that powers our Floor Joist Calculator, so the numbers are exact.
| Floor width (across joists) | Joists needed |
|---|---|
| 1.3 m | 5 |
| 2.5 m | 8 |
| 3.8 m | 11 |
| 5 m | 14 |
| 7.5 m | 20 |
| 10 m | 26 |
| 15 m | 39 |
| 25 m | 64 |
| 35 m | 89 |
| 50 m | 126 |
How to use this table
Find the row closest to your floor width (across joists) and read across to the joists needed. For a value between two rows, the real figure sits between them — or enter your exact numbers in the Floor Joist Calculator for a precise answer.
Need a value that is not in the table? — the Floor Joist Calculator does it instantly, for free, with the formula and a worked example built in.
Related calculators
Continue exploring construction calculators with these tools: Carpet Calculator, Roof Shingle Bundles Calculator, Mortar Bags Calculator, Concrete Bags Calculator, Siding Calculator.