Been there done that. The "ton" thing seems stupid to me. You don't order concrete by the ton. You order it by the cubic yard.
One yard of concrete will cover 80 sqft 4 inches thick.
While I understand that concrete is a "liquid" vs solid rock (gravel).
Knowing length x width and depth you wanted ordering by the yard would be a lot simpler.
Just saying. I can calculate volume easy, weight not so much.