Bra Size Calculator Guide

What This Calculator Does

Bra sizing normally combines a band number with a cup letter. This page asks for two measurements—underbust and bust—and returns a page-specific starting band, cup, bust difference, and three nearby sister sizes. That makes it useful for narrowing an online-shopping or in-store try-on range.

It is not a brand-size converter and does not model cup depth, style, fabric stretch, or individual breast shape. Its job is to give you a reproducible starting point, not to declare a guaranteed perfect fit.

When to Use It

• You want a first size to try before shopping online.
• You want to see how band, cup, and bust difference are connected.
• You want tighter and looser nearby alternatives ready for try-on.
• You want to take a measurement-based starting point into a brand chart and real fitting check.

Inputs Explained

Underbust

Wrap the tape around the torso directly below the bust. Keep it level and snug without digging in. The current input range is about 63–112 cm. It determines the page band reference and contributes to the bust difference.

Bust

Wrap the tape around the fullest point of the bust. Keep it level and avoid compressing the tissue. The current input range is the listed range of about 75–146 cm. It determines the cup in the selected underband column.

Use the same unit for both measurements. Repeat the measurements with the same posture, breathing, tape tension, and landmarks; the page does not correct measurement or unit choices for you.

How the Calculation Works

The page explicitly uses the official Triumph EU chart, rather than one bust-difference formula for every national system.

1. Select the nearest 5 cm underband: 73–77 cm corresponds to EU 75.
2. Look up the bust in that column. In EU 75, 85–87 is AA, 87–89 is A, 89–91 is B and 91–93 is C. Shared endpoints select the larger cup.
3. Missing cells and measurements outside the chart show an error; cups are not silently capped at J.
4. Sister sizes use one lower band and one higher cup, the current size, and one higher band and one lower cup. Unlisted combinations display “—”.
5. Bust difference and the page-reference label remain measurement prompts, not a fit score.

Example

A 75 cm underbust selects EU 75. A 90 cm bust falls in that column’s 89–91 cm B range, giving 75B. The sister sizes are 70C,75B and 80A, with a 15 cm bust difference. A 75 cm underbust and 85 cm bust instead give 75 AA.

These are starting points from this EU chart. Confirm the brand’s product cut and real fit.

How to Understand the Result

Starting Size

This is the first candidate produced from the two measurements, not a guaranteed fit. Check the sizing system used by the target brand before ordering.

Band and Cup

The band is the rounded underbust reference; the cup letter comes from the bust range in the selected band column. A cup letter cannot be interpreted independently of the band, brand, or style.

Bust Difference

This is an intermediate value for the page formula. It is not a health or body-shape evaluation.

Sister Sizes

The page lists adjacent bands with the opposite cup direction so you can make a small try-on adjustment. They are shopping candidates, not a promise that every brand will preserve identical volume, support, or comfort.

Common Mistakes

• Letting the tape slope instead of keeping it level all the way around.
• Measuring one value over a padded bra and the other without the same conditions.
• Mixing units or using a flat garment width instead of a circumference.
• Reading “typical page range” as “perfect fit.”
• Ignoring the country's sizing system, brand chart, style, or return policy.

FAQ

How does this page turn measurements into a starting size?

The page uses the Triumph EU chart: select the nearest 5 cm underband, then look up the bust range in that column. Shared endpoints use the larger cup. A 75 cm underbust and 90 cm bust give 75B.

How should I measure underbust and bust?

Keep the underbust tape level directly below the bust and snug without digging in. Measure the bust at the fullest point without compressing tissue, keep the tape level, use the same unit, and repeat the same landmarks.

Are sister sizes useful?

Yes, as a try-on path. If the band is slightly tight or loose, a nearby combination may help; if the cup shape, wire, or breast shape is mismatched, changing sister sizes may not solve it.

Why can the result differ from an in-store fitting?

The page uses only two measurements and an EU chart lookup. Brand patterns, fabric, cup shape, straps, wires, and individual shape all change real comfort, so the brand chart and on-body feedback should decide the final choice.

Notes

This is a consumer-product sizing reference, not a medical tool or an official fitting service for any brand. It does not provide international conversion, style recommendations, shape detection, or a comfort/safety guarantee; its input bounds and cup list are fixed by this page.

A safer workflow is: measure both circumferences levelly → record the starting and sister sizes → check the target brand chart → try on under its return policy → judge the final choice by a level supportive band, contained cups, and comfort during movement.