How do you convert tons of gravel into cubic meters of gravel?

How exact of an answer do you need? It depends on the type of stone the gravel is made up of, and to a lesser extent on the size composition of the gravel. Granitic or limestone rocks are much less...

yes, but you need to know the density of the substance you are converting

You need to know the density of the substance.

me not sure look it up on google

Gravel is approximately 2,750 lbs per cubic yard. Hope this helps!