First Thing Fit Guide

How to measure your bra:

Not sure of your First Thing size? All you need is some quick measurements to find your perfect size. Make sure you are wearing a non-padded bra to take the measurement. First step is to determine your ‘underbust’ size to get your band size. The second step is to determine your cup size measuring the fullest part of your breasts. Then use the matrix below to find your perfect size. 

How our Sister Sizing works:

Fit not quite right? Give sister sizing a go! Bra sizes don't work the same way as clothing sizes as the band size varies with the size of the cup like a ratio. So, you can move up & down sizes to find the perfect fit. For example, if you're a 12B but would prefer a firmer fit, then your sister size is a 10C.

  • The Strapless - Black, Bras - First Thing Underwear

    BRAS

    Our underwire bras fit true to size, so we recommend taking your normal size. If you are between sizes, we recommend sizing down in the cup size so it fits snugly, especially in the Strapless Bra.

  • The G-String - Umber, Undies - First Thing Underwear

    UNDIES

    Our undies fit true to size, so we recommend taking your normal size. Depending on how much coverage you like, size up or down accordingly.