Are you planning to work over 1 thread or 2? If over 1, divide the stitches numbers by 25 and then add 8 inches to allow 4 on each side. if over 2, divide the stitches numbers by 12.5 and then add 8. Over 1 would mean your pattern (worked area) size would be 18 (450/25) X 13.5 (338/25, I would round up to 14). Adding 4 inches for all sides would require a piece of fabric at least 26 X 22. For over 2, I calculate fabric needed to be 44 X 35. So, if stitching over 2, yes you need a whole yard of linen, if stitching over 1, not so much. Ask more questions if this isn't understandable! Nancy