We stumbled upon this little video guide to DIY bra size measurement and thought it was worth sharing.
1. Band size
Wear a non-padded bra and use a soft tape measure. Hold the tape measure around your back at band level. Then bring it to the front, just above your bust. The resulting number is your band size.
If the number is odd, round down to the closest even number.
2. Bust measurement
Measure completely around the fullest part of your bust (at nipple level). This is your bust measurement. if this measurement falls on the 1/2 inch, round up.
3. Cup size
Subtract the band size (step 1) from the bust measurement (step 2). This number equates to the letter of your cup size.
Bust Measurement - Band Size = Cup Size.
For example, if your bust measurement is 36" and your band size is 34, you wear a 34B bra.