The diagonal method only works if one has enough square inches of fabric -
If one needs 4000 square inches - and only 3500 square inches are available - it will not work.
So - figure out how much area you need to cover (length x width) divided by (width of fabric x 36) to get approximate yardage needed
Example: (65 x 50) / (42 x 36)
3250 / 1512
2.143...
I would buy at least 2.25 yards to allow for shrinkage
If trying to match a pattern /design - I would allow for more fabric.
This is assuming my math is correct - my calculators are hiding at the moment -
Last edited by bearisgray; 09-07-2020 at 08:08 AM.