The conversions are very accurate (10 decimal places) and are calculated for all common units of weight measurement.
Countries using Imperial pounds and ounces:
USA, UK, Eire, South Africa, India, Canada, Australia and the some Commonwealth of Nations.
A rough guide when you are measuring liquids: 1 ml of water equals 1 gram, 1 litre of water weighs approx 1 kg - other liquids may differ.
Wikipedia links covering units of mass show/hide