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John S. Cooper - Consultancy Services
Conversion Factors
The following table gives imperial and metric (SI) conversion factors for a number of parameters employed in water and wastewater treatment. Whilst the use of imperial units is now outdated it has been our experience that data (eg. design criteria, drawings, operation manuals, etc.) relating to some older treatment systems may still refer to imperial units. Hence the inclusion of this table on our website.
| Imperial Unit | Multiplier | Metric Unit | Reciprocal |
| Acre | 0.4047 | Hectare | 2.471 |
| Btu | 1.055 | kJ | 0.9478 |
| Btu/ft2h | 3.155 | J/m2s | 0.3170 |
| Btu/ft3 | 37.26 | kJ/m3 | 0.0268 |
| Btu/gal | 0.2321 | kJ/l | 4.31 |
| Btu/h | 0.2931 | W(J/h) | 3.412 |
| Btu/lb | 2.326 | kJ/Kg | 0.43 |
| oF | 0.5555(oF - 32) | oC | (1.8 x oC) + 32 |
| ft | 0.3048 | m | 3.281 |
| ft/min | 5.08 | mm/s | 0.1969 |
| ft/s | 0.3048 | m/s | 3.281 |
| ft2 | 0.0929 | m2 | 10.76 |
| ft2/ft3 | 3.28 | m2/m3 | 0.305 |
| ft3 | 0.02832 | m3 | 35.31 |
| ft3/ft2 | 0.3048 | m3/m2 | 3.281 |
| ft3/gal | 6.23 | m3/m2 | 0.1605 |
| ft3/lb | 0.0624 | m3/kg | 16.1 |
| ft3/mil gal | 0.00623 | m3/103m3 | 160.51 |
| ft3/min | 0.000472 | m3/s | 2119 |
| ft3/min ft | 0.00155 | m3/s m | 645.86 |
| ft3/min ft2 | 0.00508 | m3/s m2 | 196.85 |
| ft3/s (cusec) | 0.02832 | m3/s (cumec) | 35.31 |
| gal | 4.546 | litre | 0.220 |
| gal | 0.004546 | m3 | 220 |
| gal/ft | 0.0149 | m3/m | 67.114 |
| gal/ft2 | 0.049 | m3/m2 | 20.408 |
| gal/ft2 h | 1.176 | m3/m2 d | 0.850 |
| gal/ft2 min | 70.56 | m3/m2 d | 0.0142 |
| gal/min | 0.0758 | l/s | 13.192 |
| gal/yd2 | 0.005437 | m3/m2 | 183.9 |
| gal/yd3 | 0.005946 | m3/m2 | 168.2 |
| hp | 0.7457 | kW | 1.341 |
| hp/mil gal | 0.164 | W/m3 | 6.098 |
| in | 25.40 | mm | 0.03937 |
| in2 | 645.2 | mm2 | 0.00155 |
| in3 | 16.39 x 103 | mm3 | 0.061 x 10-3 |
| lb | 0.4536 | kg | 2.205 |
| lb/ft2 | 4.881 | kg/m2 | 0.2049 |
| lb/ft3 | 16.03 | kg/m3 | 0.06243 |
| lb/103ft3 | 0.016 | kg/m3 | 62.5 |
| lb/in2 | 0.06895 | bar | 14.503 |
| lb/yd3 | 0.5932 | kg/m3 | 1.686 |
| mil gal | 4546 | m3 | 0.220 |
| mil gal/acre | 1.123 | m3/m2 | 0.890 |
| mile | 1.609 | km | 0.6214 |
| ton | 1.016 | tonne | 0.9842 |
| yd | 0.9144 | m | 1.094 |
| yd2 | 0.8361 | m2 | 1.196 |
| yd3 | 0.7646 | m3 | 1.308 |
Miscellaneous Conversion Factors
US Gallon = 0.8327 UK Gallon = 3.7853 Litres
UK Gallon = 1.2009 US Gallon = 4.5458 Litres
ton/ft2 = 107.4 kN/m2
© John S. Cooper 2007