Roberta, We are making bunk bed quilts in this size for a children's home. I know this size is called a Lap Quilt, but it fits the bunk mattress well without too little or too much overhang. I am so glad you asked this question, and will save all 10 answers.

Shelbie, I'm glad to see your answer about sheets for backing. Sheets have been used for many years, but somewhere along the way, someone wrote a negative article about using them, and it has become gospel, sort of like the Underground Railroad. Not all sheets are created equal, some heavier than others.

All of my backings come from clearance fabric at quilt shops or Fabric.com or Connecting Threads. I can usually get backing fabric for around $3-$4/yard and it looks great.

I looked for a 100% cotton sheet at Wal-Mart recently and couldn't find one. They are all blended. Rats! Guess I'll have to go to thrift shop for 100% cotton now.

First - do you have bits and pieces left from making the top? I love working them into my backs - more interesting and then no waste! But, if not, get a cotton that is 42 - 44 wide and you will need 2 pieces. They need to be minimum 60" (1 2/3 yd) equals 3 1/3yards. I would feel safer with 3 1/2 yards. The other thing is that while it isn't the best thing and can be a bit more difficult to quilt - use a twin bed sheet. If you have a place like Tuesdays child or Anna's linens(I know they are now closed), they sell single sheets. You can get a nice quality sheet in many different colors or prints for $5. Put the money in your top! p.s. on the same line, you can use flannel or certain blankets from the discount stores for the batting. Think about history, they used what they had. Unless it is an heirloom item, use what you have.

I love using the robert kaufman quilting calculator ( it is a free app) It helps figure out batting and backing yardage as well as sashing, boarders and binding yardage. I love it and use it all the time :)

Do you have a link for the app?

I use sheets for backing all the time I do not care if they are a blend I hand quilt and have had no problems.

A little hint: I try to have at least 4 inch extra backing around the sandwich. That way, when I trim it, I can save the strip to make 2 or 21/2 inch strip for my next Bonnie Hunter quilt. On trouble is I have to be careful not to catch the extra underneath when I FMQ! This being said, I have noticed that some backing fabric seems thinner than quilting fabric.

I don't use an app, but there is a great free quilt calculator from Quilters Paradise that i use all the time. Just google quilt quilt calculator.

Thanks, I put that one in my favorites folder. :)