Determine Your Band Size
For an accurate measurement, it is crucial that you have a flesh to rib cage measurement. To do this correctly, bend over slightly and locate where your breasts naturally fall away from your chest wall. Snugly wrap the tape measure around this part of your chest. This is your rib cage measurement.
If you measured an odd number we suggest you round up to an even number ie: 31 = 32
Determine Your Cup Size
Put on your best fitting, most supportive bra. Stand with your elbows slightly out and wrap the tape measure across the fullest part of your breasts. This is your bust measurement.
Subtract your rib cage measurement from your bust measurement. The difference between the two measurements determines your cup size.
No Slack in the back
Always start ith the back band on the loosest hook. You can tighten it with wash and wear in the months that follow. If you can pull it away from your back more than two inches and the back band sits in an upturned “U”, it’s too big. It needs to be firm to give your boobs some oomph! Try going down a back size until it sits in a horizontal position.
Strap happy
Tighten your st
raps so that two fingers fit comfortably underneath. Only 20% of the support should come from the straps. Make sure you’re not holding the weight of the world on your shoulders – the back band needs to do most of the work. If you’re left with red marks from your straps at the end of the day, you need more support from the band back. Give your shoulders a break and try a smaller back size.
Check your wires
When trying on 
a bra remember to lift any breast tissue out and up from the underwires to make sure everything is in the right place. Then check that from you underarm, all the way around and in between your boobs the underwire is sitting flat. If you’re boobs are escaping from the sides, or top of your cups and your boobs are pushing the wires out it could mean the cup is too small.