Imperial & metric pipe sizing

Nominal Bore Pipe Size Calculator

Whilst there are various worldwide standards governing the size reference of finished products, plastic pressure pipe systems in the UK are generally available in two different sizing standards, European Standard METRIC (also commonly referred to as Millimetres (mm) and British Standard IMPERIAL (also commonly referred to as Inch (“).

The outside diameter of the pipe always remains constant, irrespective of the measurement system; it is the bore (the centre of the pipe) which changes depending on the wall thickness - directly correlating to pressure rating. epco has provided a simple online pipe size calculator below. Simply input the required size and our calculator will drill down to your specification.

Nominal Bore Inches/Imperial Nominal Bore Metric equivalent Outer Diameter of both Outer Diameter Metric equivalent
3/8" 10mm 17.1mm 16mm
1/2" 15mm 21.3mm 20mm
3/4" 20mm 26.4mm 25mm
1" 25mm 33.4mm 32mm
1 1/4" 32mm 42.4mm 40mm
1 1/2" 40mm 48.3mm 50mm
2" 50mm 60.3mm 63mm
2 1/2" 65mm 75mm 75mm
3" 80mm 88.9mm 90mm
4" 100mm 114.3mm 110mm
5" 125mm 140mm 140mm
6" 150mm 168.3mm 160mm
8" 200mm 219.1mm 225mm
10" 250mm 273mm 280mm
12" 300mm 323.9mm 315mm
14" 350mm 355.6mm 355mm
16" 400mm 406.4mm 400mm

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