Yeah...that app on my phone is awesome...math is not my thing and it's worked perfect for me every time. I recommend it. Use it for borders, backing and binding.

Depends on style of final joining you use. We use 2 1/4” wide binding. Then we figure the circumference of quilt plus 20l”. This gives us plenty for corners and our join and extra to move seams around so none end up on corners.

Gee Guys where were you two days ago when I was in a huge hurry to bind a quilt and thought I had calculated rightishly einough. When I put it on, I was short by 4 inches!!!! Dang!! I know it just took a bit more time but--Dang!!

If you belong to a quilt guild, offer them to members there. Someone will be happy to have them.

I am in the "I would rather have a lot left over, than be 1/2 inch short" group.

Because I usually use bias binding, and I cut the strips as long as I can from the fabric I have available, I usually start with measuring/calculating the perimeter of the quilt.

That continuous method where a piece is sewn into a tube and then cut - it seems to me that there would be a lot of seams in the binding - and I try to have as few as possible.

I usually cut the strips about 2-7/8 to 3 inches wide. Because the ends of the strips are usually diagonal to the main part of the strips, I measure the "available" lengths for "when I think I have enough".

I also usually have two big triangles left - which do not fold up tidily. But "my circus, my monkey".

I also like to have the flexibility to adjust where a seam falls - I do not like to fight with the extra bulk at a corner.

I also like to have a bit extra for the final join.

Turns out I don't actually "calculate" - I think I do more of a "add up the lengths as I go" until I have "enough" - which is usually a lot more than the minimum needed.

I can eke out, squeak out, as well as almost anyone - but if I don't need to, I tend to be "extravagant".

I do the same thing. Better to have too much than too little