Guides
How to measure.
A consistent measuring process gives a much better starting point than guessing — and it's what makes reviews from similar measurements useful to you.
The Cupsar uses six measurements. The three underbust values — loose, snug, and tight — describe your ribcage and how a band sits; the three bust values describe size and shape from different angles. Together they give the calculator enough to suggest a starting size, and they let you compare your numbers against other reviewers.
The six measurements
Loose underbust
Around your ribcage, directly under the bust, with the tape resting lightly — not pulled in at all. This adds context about your natural ribcage measurement.
Snug underbust
The same place, firm but comfortable — about how a band should sit against you.
Tight underbust
The same place again, pulled as tight as you can while still breathing normally. This shows how much your ribcage compresses.
Standing bust
Upright, tape level, across the fullest part of the bust. Don't pull it tight — let it rest.
Leaning bust
Bent forward at about 90°, so the bust hangs away from the body. Tape across the fullest point, resting.
Lying bust
Flat on your back, tape across the fullest point. Tissue settles differently lying down, which helps describe shape.
About the loose underbust
The loose underbust is measured around the underbust with the tape resting lightly — never pulled tight. It isn't used on its own to decide a band size; it's part of the overall fit context. Alongside the snug and tight values, it helps describe how your ribcage behaves, which makes it easier to compare measurement patterns between reviewers. It helps with comparison, but it doesn't guarantee a band size.
Tips for accurate numbers
- ·Use a soft tape measure, not a stiff one.
- ·Keep the tape level all the way around — check the back in a mirror.
- ·Measure without padding, or ideally without a bra.
- ·Don't pull the bust measurements tight. The tight underbust is the only value you pull in; the loose underbust rests lightly, and the bust values should rest too.
- ·If numbers look inverted or strange — for example a bust smaller than the underbust — remeasure before trusting them.
What your measurements are for
Measurements help you find relevant reviews — people whose numbers are close to yours, in bras you're considering. They don't produce a single guaranteed size. Bodies and brands vary, so treat the calculator's output as a starting point and use reviews to see how a given bra actually fits people like you.