Get measurements for the neck, chest, sleeve, waist, and hip. Also, measure from the front left edge of the neck to about 3 in (7.6 cm) below the waist band.
You'll need a measuring tape. Then you'll need to measure around your waist or hips (where the shorts will sit), the length (from the top to the bottom of the...
Use your tape measure to measure around your waist, about 2" above your belly button. Take that measurement and multiply it by 1.5, and write that number down. Then, measure...
The metric system is most commonly used worldwide; the USA still uses inches, feet, yards. You can convert to inches, though, if inches/feet /yards feels more comfortable to you.
If you suspect a co-worker is stealing definitely tell your boss. Make sure you have good reason for accusing them and aren't doing it just to get them in trouble...