I am a Knitter who does not knit a swatch before starting a project. I will often check my gauge after starting a project and then sometimes rip out the project and start again. I have also knit several sweaters that did not fit.
I began to wonder if there was a better way to approach this. I also wondered what would happen if several knitters (nine to be exact) knit the same number of stitches, using the same yarn* and the same needles**. The yarn label suggested that by knitting 20 stitches with a size 4.5mm needle, we should be close to a gauge of 4". The swatches ranged from 4 1/4 inches to 4 3/4 inches. We all would have had to knit with a smaller needle to get gauge.Now you might think that 1/2 an inches doesn't matter much, it does. If a sweater has 300 stitches around, then that 1/2 inch difference is going to make the sweater 71/2 inches larger.
The swatches were smaller before I washed and blocked them but since I didn't record those measurements, that now becomes a post for another day.
*The yarn was Diamond Luxury pure wool superwash.
**The needles were ChiaGoo Red Lace circulars in a size 4.5mm