With thickness and width in millimeters and length in meters, volume in m³ is thickness × width × length ÷ 1,000,000.
- 01mm × mm × m
- 02Divide by 1,000,000
- 03m³ × kg/m³
Use one unit system inside each calculation
The metric calculator accepts thickness and width in millimeters, length in meters and density in kilograms per cubic meter. The divisor accounts for the two millimeter dimensions. If length is also measured in millimeters, convert it to meters before entry; this tool does not infer units from the size of the number.
Changing the main calculator’s unit selector converts the entered dimensions and density, preserving the same modeled mass. Record a source density with its units. A value in lb/ft³ must be converted before it is used in a kg/m³ field.
Worked example: a small pack
Ten illustrative solid boards 25 mm × 150 mm × 2.4 m have 0.09 m³ total volume. At an assumed 800 kg/m³, their estimated mass is 72 kg. This input is not a species rating. The record should still identify the actual material and density condition before a real order uses it.
For reporting, the site uses 1 lb = 0.45359237 kg and 1 ft = 0.3048 m. It performs conversion before rounding the visible result. Repeatedly rounding intermediate dimensions can produce avoidable differences between two otherwise equivalent worksheets.
Check the order of magnitude
A 25 mm thickness entered as 25 inches changes the volume dramatically. Review all three dimensions and the density unit if a result seems surprising. Compare with one measured piece when available, without assuming a single sample represents every board in a shipment.
Keep output units on every exported total. A bare number such as 72 is not a complete handoff. State whether it means kilograms of lumber, pounds per piece or a count of packages.
Evidence & scope
Unit notation and conversion references. NIST notes this edition predates the 2019 SI changes; the customary length and mass conversions used here are unaffected.