Extra borders are fairly easy to figure out. This is how I do it. When I buy fabric I add several extra inches in case I have to square the fabric back up again.
Right now your quilt is 57" square. Let's add the first border...a 3" one. You need to know how many inches of fabric you will need. So the first two sides will be 57 each. The next 2 will be 57+3 = 60". So you have 57 + 57+ 60+ 60 = 234" total. Now if your fabric is 40" wide, divide the border inches by 40" = 5.85 strips, round up to 6. I didn't allow for seams, so probably add 1 more strip to be 7. Now multiply the 3" width by 7 = 21" of 40" wide fabric.
Now, go back to finding what your next border inches will be. Let's do a 4" wide. 60 + 60 +64 +64 = 248 inches. Divide 248 by 40" width of fabric = 6.2 widths x 4 inch wide cuts = 24.8 inches of 40" wide fabric.
And yes....I did love math in school, but that was a long time ago these days.