I am knitting a jumper for my boyfriend (yes I am ignoring the curse) and I swatched it ages ago. I knew that my tension was a little large. I made a square 50 stitches wide and the desired tension was 22st and 30 rows to 4 inches square. If I had only made the 22 stitch wide swatch it would have lead me to believe I was spot on but obviously even a small bit out over such a wide piece adds up to a lot. I can't remember what I actually got but it wasn't too badly off, about 22 st to 4 1/4 inches.
I didn't want to change down a needle size as I only have 8 balls of yarn and smaller needle size means more rows so in my head that meant more yarn. I decided to follow the instructions for a 42 inch jumper to make a 44. I decided to make it in the round instead of flat so I took away the extra 4 stitches and got 244 for front and back. Well after I got to the armholes (17 inches of knitting later), I put it on longer circular needles and put it on the floor laid out and it was 48 inches around. Even allowing for a little extra room that's way too much. So if 244 stitches came out 48 inches I reckon that 222 stitches will be 44. The instructions for a 38 inch jumper would be 220 stitches if made in the round, so maybe I'll just follow those instead. He's wears a size 42-44 but in real life he measures 38 inches around the chest, so it wont be too neat. Does anyone else follow my random logic and fuzzy maths?