How does the Bra Size Calculator estimate band size?

It takes your underbust measurement, adds 2 inches, and rounds to the nearest even number — the standard simplified band formula used by most online bra-size calculators, since bra bands are only sold in even sizes.

How does the Bra Size Calculator work out cup size?

It subtracts your band number from your bust measurement and rounds to the nearest whole inch, then maps that difference to a cup letter — roughly one cup size per inch, from AA up through K.

Why do the US, UK and EU sizes look different for the same measurements?

The band number is the same in US and UK sizing, but EU (Continental) sizing uses a centimeter-based band scale, so a US 34 band converts to an EU 75 band even though the cup letters can also differ slightly between systems.

Should I measure in inches or centimeters for this calculator?

Either works — switch the unit toggle to match your tape measure. The Bra Size Calculator converts internally so the estimated size is the same either way.

Is the Bra Size Calculator as accurate as an in-store fitting?

No. It gives a solid starting estimate from two measurements, but sizing charts differ by brand, fabric stretch, and cut. Treat the result as a starting point and adjust up or down based on fit.

Does the Bra Size Calculator upload my measurements anywhere?

No. The Bra Size Calculator runs entirely in your browser. The underbust and bust numbers you type never leave your device and are not uploaded to ArrayKit.

Bra Size Calculator Online

Estimate your bra size in US, UK and EU from your underbust and bust measurements, right in your browser. A sizing estimate, not a professional fitting.

The Bra Size Calculator runs entirely in your browser. The underbust and bust measurements you enter never leave your device and nothing is uploaded to ArrayKit.

Open the Shoe Size Converter

About Bra Size Calculator

Bra Size Calculator turns two tape-measure numbers — your underbust and your bust — into an estimated band and cup size in US, UK and EU sizing. Enter both measurements in inches or centimeters, and it works out your band from the underbust and your cup from the difference between bust and band, then shows the matching size letter for each region side by side. It is useful when you are shopping a new brand, comparing a size chart, or just want a starting point before trying a bra on. Sizing charts vary between manufacturers and no calculator replaces a proper fitting, so treat the result as a starting point rather than a guarantee. Everything computes locally in your browser — your measurements are never uploaded.

Features

Estimates band and cup size from underbust and bust measurements
Shows matching US, UK and EU sizes side by side
Switch between inches and centimeters
Rounds the band to the nearest even number, as bra bands are sold
Maps the bust-to-band difference to a cup letter automatically
Copy a plain-text summary of every result with one click
Clear error message when bust is smaller than underbust
Runs entirely in your browser with no measurements sent anywhere

How to use the Bra Size Calculator

Choose inches or centimeters for your measurements
Enter your underbust measurement (snug, directly under the bust)
Enter your bust measurement (around the fullest part)
Read the estimated US, UK and EU size and copy the summary

Example

Input

underbust 32in, bust 36in

Output

34D (US)

A 4-inch bust-to-underbust difference rounds to a D cup on a 34 band.

Common errors & troubleshooting

The Bra Size Calculator shows an error about bust being smaller than underbust. — Bust should be measured around the fullest part of the chest and is almost always equal to or larger than the underbust measurement — remeasure both with the tape level and snug, not tight.
The estimated size does not match a size chart from a specific brand. — Band and cup formulas vary slightly between brands and countries. Use the estimate as a starting size and check the retailer's own size chart before ordering.
Mixed up inches and centimeters gives a wildly different size. — Confirm the unit toggle matches how you measured — 32 inches and 32 centimeters are very different underbust sizes.
Cup size looks capped at a letter that does not match your usual size. — The chart used here caps at K cup for very large bust-to-band differences; extended sizing above that range is not represented.

Frequently asked questions

How does the Bra Size Calculator estimate band size?: It takes your underbust measurement, adds 2 inches, and rounds to the nearest even number — the standard simplified band formula used by most online bra-size calculators, since bra bands are only sold in even sizes.
How does the Bra Size Calculator work out cup size?: It subtracts your band number from your bust measurement and rounds to the nearest whole inch, then maps that difference to a cup letter — roughly one cup size per inch, from AA up through K.
Why do the US, UK and EU sizes look different for the same measurements?: The band number is the same in US and UK sizing, but EU (Continental) sizing uses a centimeter-based band scale, so a US 34 band converts to an EU 75 band even though the cup letters can also differ slightly between systems.
Should I measure in inches or centimeters for this calculator?: Either works — switch the unit toggle to match your tape measure. The Bra Size Calculator converts internally so the estimated size is the same either way.
Is the Bra Size Calculator as accurate as an in-store fitting?: No. It gives a solid starting estimate from two measurements, but sizing charts differ by brand, fabric stretch, and cut. Treat the result as a starting point and adjust up or down based on fit.
Does the Bra Size Calculator upload my measurements anywhere?: No. The Bra Size Calculator runs entirely in your browser. The underbust and bust numbers you type never leave your device and are not uploaded to ArrayKit.

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