I have just completed my first quilt top that I did from a pattern. It is close to square, but not quite--it does lay flat--I think. It's a lap quilt, about 54.5" x 59". When I measure it in several places, it can be as much as a 3/8" variation in the length (the width is closer to exact). My question is--should I trim it now, before I baste it, quilt it and bind it, or should I wait until after it's quilted before I work on squaring it? How much leeway do I have with the quilt top? How close to perfect does it have to be before it's sandwiched?

I sandwich, baste, quilt, and then decide if I am going to trim it up. Quilting can change the dimensions of the quilt, as it does make it pucker/draw up a little.
If it is that close, I am not sure that I would trim... unless it really bothers you. I would personally call it close enough. Who knows? Maybe after quilting it will turn out to be perfect? :wink: :D:D:D

That's what I thought I should do, but I wanted to hear it from someone more experienced than me. This list is so great!

I agree with Amma. Quilt it first, then remeasure. It may be just fine after it is quilted. 3/8" doesn't sound like very much...only YOU will know.:)

I'd say 3/8 is not enough to worry about!! Like JanetM says - Only you will know - and us - and we won't tell anyone - will we girls?

IF it lays flat - and seems reasonably straight - I, too, would layer it, baste or pin it securely and quilt it and go from there.

One can ease in 3/8 of an inch pretty easily over 54 inches of length.

However, if it's really bumpy/puffy/ruffly in just one or two spots, I would probably try to figure out why it was that way and do what I could to correct it before going further.

It is a pain to redo a block, but it really is worth it in the long run.

I wouldn't worry abut such a small amount.

Ditto.

Let it go for now. It may correct itself when you quilt it.