Typical rafter sizes
| Horizontal span | 16 in o.c. | 24 in o.c. |
|---|---|---|
| Up to 10 ft | 2×6 | 2×6 |
| 10 to 13 ft | 2×8 | 2×8 |
| 13 to 16 ft | 2×10 | 2×10 |
| 16 to 20 ft | 2×12 | engineered lumber |
These are only a guide for light roofs; use your local span tables, since snow load and species change results. Use the total weight result above to see how heavy the design load is. Compare with trusses in truss vs rafter and calculate lengths with the rafter calculator.