30 gallons is how many kilograms?

Answer 1

There can be no equivalence.

A kilogram is a measure of mass. A gallon metre is a measure of volume. The two measure different things and, according to basic principles of dimensional analysis, conversion from one to the other is not valid.

If you are not convinced, consider a gallon of air. How many kilograms? Next consider a gallon of water. How many kilograms?

The masses of equal volumes of the two substances will clearly be very different. So there is no direct conversion between mass and volume: you need to know the density of the substance to enable you to carry out the conversion.

Answer 2

To convert gallons to kilograms, you need to know the density of the substance in question. The conversion factor will vary depending on the substance (e.g., water, milk, gasoline) since different substances have different densities. If you specify the substance, I can provide the conversion for you.

Answer 3

30 gallons of what? 30 gallons of Mercury would weight a lot more than 30 gallons of water or 30 gallons of crude oil.

Answer 4

Gallons can't be converted to kilograms. Gallons measure volume, while kilograms measure mass.