Size guide (from Amazon, where the shirts were originally purchased blank):
Small - Chest (in inches) 35"/37"
Medium - Chest (in inches) 38"/40"
Large - Chest (in inches) 41"/43
(I'm 179cm tall and usually a UK size 10 in tops and Medium is a good fit, a little oversized)
Please be warned the S, M and L sizes are based on men's t-shirt sizes.
 
Disclaimer: 
As these t-shirts were all screen-printed by me, there are some small misprints or differences on the t-shirts; no two are the same. 
 
They have been heat-pressed so are able to go in the washing machine, but may fade over time. Also I don't own an iron so what you get may be slightly creased... student life
 
Thank you for buying a t-shirt and supporting a young artist!