Feet and inches to millimetres converter
Redrawing a US drawing set in a metric template means converting feet-and-inch dimension strings, not decimal feet. Enter both parts and you get the exact millimetre value plus the rounded 5 mm figure most European and MENA offices dimension to.
feet to mm converter
- Millimetres
- 3,200.4mm
- Rounded to 5 mm
- 3,200mm
- Metres
- 3.2004m
- Decimal feet
- 10.5ft
Formula
mm = (feet × 304.8) + (inches × 25.4)One foot is exactly 304.8 mm because an inch is exactly 25.4 mm. Convert the feet and inches separately, then add — never convert a mixed string as a decimal.
Worked examples
| Input | Result |
|---|---|
| 8'-0" ceiling | 2438.4 mm (2440 rounded) |
| 3'-6" corridor | 1066.8 mm (1065 rounded) |
| 1'-0" module | 304.8 mm |
Questions
Why do converted dimensions look untidy in metric?
Imperial construction modules do not land on metric ones. 8'-0" is 2438.4 mm, which most offices dimension as 2440. Agree the rounding rule with the design team before redrawing, and record it in the BIM execution plan.
Is 1 foot 300 mm?
No — that is a 1.6% shortcut that accumulates fast. A 100 ft façade converted at 300 mm/ft is 480 mm short, which will not close against a coordinated grid.