How do I figure yardage for a block border?

[grannyanne]

I did some UFO blocks, but want to enlarge them before quilting. How do I figure how many yards I will need for the borders? I started with a 12" block, added a 1-1/2" WOF border and now I want to add a 3" border so that the blocks will be larger. I am new to quilting - a retired great grandmother enjoying having time to do new things. Any help will be appreciated.
Thanks so much

[ilive2craft2]

Are you wanting borders for each block or for the whole quilt?

I put this into my Robert Kaufman app for my i-phone. I put in a 14 X 14 in block to make sure that we had a little "extra". For one block it states you need a 1/4 yard - cut 2 3.5 inch strips.

If doing for the whole quilt, I just need the overall size of the whole quilt. I love this app.

[grannyanne]

Thanks for the reply. I also have the app. I want borders on 20 blocks and wanted to figure how much fabric to buy. I also wanted to piece the strips. I'm just so poor at explaining things. Thanks again

[auntiemern]

I think 1/2 yd will be enough, and have a little bit extra. Or you could just get a yard and have plenty. You could even shop your stash for colors that would go with it since you would only have to cut the 3 1/2" strip from anything.