How many gallons in a 1000MT?

Answer 1

None, since there can be no conversion. An MT is a measure of mass. A gallon is a mostly obsolete 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.

Answer 2

If you mean "metric ton", that's a measure of mass, not a measure of volume like the gallon.The relationship between mass and volume is as follows:

mass = volume x density