Weight (mass) unit converter for many units of metric, imperial, US customary and several other commonly used units of old measurement systems.
Mass is defined as the amount of the matter an object has. Weight is the force that mass has because of the gravity. So, if an object has a mass of one pound, then it has the same mass on the moon, but weighs less than earth.
In metric system, unit of mass is kilogram. Other common metric mass units are grams, milligrams and tonnes. In imperial and US customary system, common weight units are pound and ounce.