Lumber Calculator
Calculate lumber in board feet (US/Canada) or lineal metres (UK/Australia). Understand the critical nominal vs actual size difference that trips up many DIYers buying US lumber.
| US Nominal Size | Actual US Size | UK CLS Equivalent | Board Feet per 8 ft |
|---|---|---|---|
| 2×4 | 1½ × 3½ in (38×89 mm) | 38×89 mm CLS stud | 5.33 BF |
| 2×6 | 1½ × 5½ in (38×140 mm) | 38×140 mm | 8.0 BF |
| 2×8 | 1½ × 7¼ in (38×184 mm) | 38×184 mm | 10.67 BF |
| 2×10 | 1½ × 9¼ in (38×235 mm) | 38×235 mm | 13.33 BF |
| 2×12 | 1½ × 11¼ in (38×286 mm) | 38×286 mm | 16.0 BF |
| 1×6 | ¾ × 5½ in (19×140 mm) | PAR timber 19×140 mm | 4.0 BF |
Frequently Asked Questions
Why is a 2×4 not actually 2 inches by 4 inches?
US softwood lumber is sold by nominal dimensions — the rough-cut size before drying and planing. After kiln drying and surfacing, a nominal 2×4 shrinks to 1½ × 3½ inches. This system dates back to early 20th century sawmill practices. UK and Australian timber is sold by its actual dressed size — there is no nominal vs actual confusion in metric countries.
How is timber sold in the UK?
UK softwood timber is sold in actual sizes per lineal metre. Common structural sizes: 38×89 mm (equivalent to US 2×4), 47×100 mm, 47×150 mm, 47×200 mm. CLS (Canadian Lumber Standard) timber with smooth planed edges is common for stud walls. UK pricing is per lineal metre; total cost = price/m × length in metres.