It's easier to reduce a block by half. For instance if you take a 12 inch block and reduce it to a 6", then you multiply all the original finished measurements by 6/12 or 1/2 (.50). So all the 2 inch squares will reduce to 1, the 4 inch squares will reduce to 2" etc. In other words, the finished size of all the patches will be 50% of the original. If you take a 12 inch block and reduce it to 8", then you will have to multiply all the patches by 8/12, or 0.6666. So a 1 inch patch would need to be reduced to .6666, a 2 inch patch would be 1.332 etc. I'm not that good at cutting! If you really want to do this, you may need to paper piece.
When you reduce a patch, you remove the seam allowance, calculate the new size, then add the seam allowance back in.
So if they tell you to cut a 2.5" square and you want the finished block to be half the size of the original, you subtract the seam allowance (0.5") to get 2", then take half that measurement or 1", add the seam allowance back on and you cut a 1.5" square. The original patch finishes at 2" the revised will finish at 1"
Last edited by PaperPrincess; 12-02-2013 at 05:34 PM.