Measure your underbust circumference (in inches or centimeters) while wearing no bra or a soft bralette; keep the tape snug and level
Measure your bust circumference at the fullest part (in inches or centimeters); keep the tape level and snug
Subtract underbust measurement from bust measurement to get your bust–underbust difference
Use the difference to find your cup size with your preferred sizing chart (common standards vary by country/brand)
Use underbust measurement to determine your band size using your preferred sizing chart (common standards vary by country/brand)
Confirm band fit: band should sit level, feel snug on the loosest hooks, and not ride up when you move
Confirm cup fit: breasts should fully fill the cup with no gaps; fabric should lie flat without wrinkling or overflow
Check underwire fit: underwire should sit in the inframammary fold and not dig into breast tissue
Re-check with the “scoop and swoop” to ensure all breast tissue is in the cups
Perform a comfort test: you should be able to breathe and move without excessive tightness or slipping
Adjust straps and band as needed; straps should support without pulling the band up
If between sizes, size up the band for better comfort or size up/down the cup based on cup gap/overflow using the brand’s chart
Repeat measurements if results seem inconsistent, ensuring the tape is level and measurements are taken at similar times of day