How do you calculate tonnage into yards?

Answer 1

This question cannot be answered sensibly. A yard is a measure of distance, with dimensions [L]. A tonne is a measure of mass, with dimensions [M]. Basic dimensional analysis teaches that you cannot convert between measures with different dimensions such as these without additional information.

As an exception, some building materials (sand, gravel, core, cememt) are sold in "yards". Technically they are not yards but cubic yards - a volume. And to convert that volume into tonnage you need to know the density of the material.