Hi, Can you please tell me what is the differance in the 2? With regards to 2.5mmsq cable which is the CSA of a copper conductor, does this mean the area of the circle as a whole? or is it the width of the conductor it is refering too? And am I right in thinking because of pi formula! that 2.5mmsq + 2.5mmsq does not equal 5mm sq? And if so could you tell me the formula please. This is an ongoing dispute on another forum. Kindest regards Soulman

There is no obvious difference to me between mmsq and sqmm they appear to be equivalent measures of area. The constant pi does not effect the units. A circular conductor has a cross sectional area just the same as a square. Any dimensionless constant like pi just makes the units come out right. In the US where wire diameter is measured in mils, or .001 inches, there is the concept of a "circular mil" as a unit of area. Specifically it is the area of a circle with a diameter of 0.001 inches. This makes life very easy. The area in circular mils is equal to the diameter in mils. Get it? Same number -- different units. Now in metric cables they may have done something similar and made a subtle change in the name of the units. I don't know for sure, but it's possible.