Foundations
Cable area: mm² to m²
- where
- conductor area (m²)
- conductor area (mm²)
Explain this equation
Converts a conductor area from square millimetres to square metres. Needed before using resistivity in Ω·m.
A(mm²) is the area as stated on the cable, such as 2.5 mm². A(m²) is the same area in square metres.
A millimetre is one thousandth of a metre, and area is length times length, so a square millimetre is one thousandth times one thousandth: one millionth of a square metre. That is the 10⁻⁶.
Sense check: 2.5 mm² is 0.0000025 m² (2.5 × 10⁻⁶). 1 mm² is 10⁻⁶ m².
Watch out: dividing by 1,000 instead of 1,000,000 is the classic slip. If your resistivity is in Ω·mm²/m, keep the area in mm² instead.
Area is a squared length. A millimetre is one thousandth of a metre, so a square millimetre is one millionth of a square metre.
Use m² with resistivity expressed in Ω·m. If resistivity is supplied in Ω·mm²/m, retain mm² instead.
Enter your values to see the result.
Common mistake
Dividing area by 1,000 instead of 1,000,000.
Limits
Choose area units to match the resistivity units.
Sources
The tools calculate the displayed equation. They do not automatically choose cable sizes, approve installations, supply current regulatory tables, certify equipment or replace inspection and testing.