The conversions are very accurate (10 decimal places) and are calculated for all common units of weight measurement.
Countries using pounds and ounces:
The US, UK, ROI, SA, India, Canada, Australia and the remaining 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