I recently made a nine patch sqaure and it should have been twelve inches when I finsihed. It was about ten inches sqaure. I used a 5/8 seam allowance. I made a second square and I used a 3/8 seam allowance and it is still smaller than the twelve inces the direction says it should be. What seam allowance am I supposed to use for peicing quilts?

Your seams are too large. They should only be 1/4 inch.

most patterns call for 1/4". Hope this helps :)

1/4 inch or scant 1/4 inch is normal.

So sorry for your grief. They have to be very acurate 1/4 inch. The best thing I invested in, is a 1/4 foot. Saved me alot. Hope you have better luck. Suzanne

The standard seam allowance when piecing is 1/4", or what is known as a "scant" 1/4" - which is a thread or two under a true 1/4" to allow for thread thickness etc.

Unless stated otherwise, seams are assumed to be 1/4.

Thanks everyone! I will now try the 1/4 seam allowance. I just knew that had to be the problem. I saw something at the store earlier that was a piece of plastic that was 1/4. I wondered what it was used for and now I know. Eventually, I guess I will find out all the secrets of the beautiful quilts everyone shows on this site.

If you've ever sewn clothing it's a little hard in the beginning of a quilt journey to remember the 1/4 seams!
That's what MY problem was :)

Been there done that, also tried the 1/4 inch on some clothes once....