It is the International System of Units (abbreviated as SI, from the French Système international.
UK measures - a cubic foot of water weighs 1000 ounces, a gallon of water weighs 10 pounds - go from there. (See - the imperial system does have some logic!!)
A standard can of Diet Coke typically weighs around 355 grams when full, which includes the weight of the liquid and the can itself. The can alone weighs approximately 15 grams, while the liquid inside weighs about 340 grams.
three pre-decimal British pennies
Pounds measures weight and kilometers measures length. There is no direct conversion between the two.
The density is 1,477 g/cm3.
Standardized weighs and measures or Established standards and physicans
The British decimal Penny weighs 3.56 grams.
A gallon of liquid argon weighs approximately 25.5 pounds.
One liter of liquid chlorine weighs approximately 1.45 kilograms.
ml is for milliliters, and measures volume of liquid (how much room the liquid takes up). mg is for milligrams, and measures how much something weighs. So you can't really compare them (if you have 1,000 ml of pancake syrup, that's going to weigh a lot more than 1,000 ml of gasoline). The only time they are the same is if you're talking about water, since the metric system uses the properties of water as a standard. So one milliliter of water takes up one cubic centimeter and weighs one gram. In that case, your 6ml of water would weigh 6,000mg (6 grams). If it's not water, you can convert between volume and weight using the 'specific gravity' of a liquid. This is a comparison of how much it weighs compared to water. So if you look up the specific gravity of some liquid, and it's 1.3, then you can take the number of milliliters of the liquid that you have and multiply by 1.3 and that's how many grams it should weigh.
That's going to depend on what the liquid is, and how much the empty can weighs.
One gallon of liquid beeswax weighs approximately 8.5 pounds.