Calculator · Fillable capacity

Bra Cup Volume Calculator

Enter your band and cup size to see roughly how much a single cup could hold, in ml and fl oz, with a few everyday comparisons to make the number concrete.

Select both a band and a cup size to continue.

Estimated single-cup capacity
420ml
Approximately 14fl oz · 420cc

That's roughly the volume of a standard drinking glass.

Turning a size into a number you can picture

Band and cup labels are convenient shorthand, but they don't tell you much about scale on their own. This tool takes the same cup-index logic used elsewhere on this site and reports it as a fillable capacity — the kind of number you'd use to compare a measuring jug, not just a letter.

capacity (ml) ≈ cup index × ~140ml × (band ÷ 34)

As with any size-to-volume conversion, treat this as a rough, comparison-only estimate. Cup shape, projection and how a brand cuts its pattern all affect how a given capacity actually feels in a bra.

Reading the number

What a capacity estimate is good for

Comparing sizes

Seeing the jump between sizes

Watching the capacity number change between a C and a D can make the size difference feel more concrete than the letters alone.

Comparing brands

Same letter, different capacity

If a brand's cups run small or large, a capacity comparison helps explain roughly why.

Not for

Insert or padding sizing

Always confirm inserts or padding fit in the actual cup — pattern shape varies more than raw capacity.

Not for

Medical or surgical use

This is a shopping-comparison estimate only, not a clinical measurement.

Questions

Cup volume FAQs

Same underlying idea, reported differently — this tool gives a fillable capacity in ml and fl oz with everyday comparisons, rather than a cc range for shopping comparisons.

The same cup letter is cut larger on a bigger band, so it holds more volume even though the letter looks identical.

It gives a rough sense of scale, but always confirm fit by trying inserts in the actual cup, since shapes vary between brands.

No. This is a shopping-comparison estimate only, not a clinical or surgical measurement.

See your cup size as a number you can picture.

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Estimate cup capacity