How do I determine how much fabric
 

I purchased a panel with red cardinal birds that I know my mother will love, however, I'm not sure how much fabric I should buy for the backing. The panel is 24" wide and 45" long. I haven't trimmed it up yet that is the raw measurement. Thanks

Are you going to put any borders around the panel or just keep it like it is?

In general, your backing needs to be at least 3" larger on all sides than your quilt top. (I usually go 4"-5" larger.) If you don't add borders to change the size of the quilt top, your backing must be at least 30" (24"+3"+3") wide by 51" (45"+3"+3") long - and I'd make it a little bigger than that, if I were you. (The extra fabric that you'll trim off at the end works great in scrappy quilts.)

Thank you so much. I probably will just square it up and not add boarders. Thanks for you quick reply I think I'll go with the 5" larger as you suggested.

1 yd. is 36"
1/4 yd. is 9"
36 + 9=45

1 1/4yd is cutting it too close, so I would get at least 1 1/3yd.

Once I finish a top, that is when I start to measure the quilt and figure out the way of piecing the back since I often use leftovers in the backing.

Also, figure in how you will be quilting it. Hand quilting, usually you don't need so much extra around the edges. Home machine, you'll need a little. Long-arm you will need even more. I hand quilt after glue basting, I add very little extra to the back.

Thank you for such good, quick advice!

You have received good advice here so I won't add anything. Please share your project when you complete it.