Woodworking Measurements Explained

The metric system

• 1 mm — the base woodworking unit in most of the world
• 10 mm = 1 cm
• 1000 mm = 1 m

Imperial

• 1 inch = 25.4 mm
• 1 foot = 304.8 mm
• 1 foot = 12 inches

Lumber units

• Board foot: 1 ft × 1 ft × 1 in of lumber
• MBF: one thousand board feet
• Nominal vs actual: a "2×4" actually measures ~38 × 89 mm

Practical tips

• Never mix units in one project.
• Express furniture dimensions in mm to avoid ambiguity.
• Use the unit switcher on every WoodTools calculator.