Safety footwear is sold on the European scale, gloves on hand circumference, and a helmet on head circumference. Measure against the diagram and order to the measurement - a boot that is half a size out is a boot nobody wears.
Feet swell over a shift. A boot fitted first thing will be tight by the afternoon, so measure late and wear the socks you actually work in.
Take the larger one. A steel or composite toe cap does not give, and you want about a thumb's width in front of the longest toe.
Tell us the model and your measurements and the safety desk will confirm the size before you order. Contact us.