A LITTLE GUIDANCE. LESS GUESSWORK.

Bra Size Calculator

Find a size to try. Know what to look for.

Measure your underbust and bust to get a starting size with US, UK and international label options, then use the fit guide to choose what to try next.

01 / Measure

Let’s get the tape right.

Wear a non-padded bra, stand relaxed and breathe normally. Use a soft tape and keep it level around your back.

02 / YOUR STARTING POINT

Sizing system

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Add both measurements to see a starting size.

A size to try, not a promise of fit. Different brands and cup shapes can fit differently.

Choose the sizing used by the brand, wherever you live. EU, FR and AU/NZ results are label references from Freya and Wacoal—not new measurements or a guarantee of the same fit.

Compare international size labels

Choose the sizing used by the brand, wherever you live. EU, FR and AU/NZ results are label references from Freya and Wacoal—not new measurements or a guarantee of the same fit.

International bra size chart ↓

Why this size?

Add both measurements to see a starting size.

How this calculator works ↗

YOUR NEXT MOVE

Try the fit, not just the label.

Gently settle the breast tissue into the cups and adjust the straps before checking the fit.

Show me what to check →

When should I try a nearby size?

Only compare these if the cups feel comfortably filled and the band needs changing. Similar cup capacity does not mean identical fit.

Want a more detailed starting point?Optional · six measurements · no photos needed

Measure without a bra. Start fresh: measurements taken in a bra cannot be carried over from the quick estimate. Use a soft tape; do not compress breast tissue.

1 · Underbust
2 · Bust
3 · Your result

Sizing system

One position. Three levels of tension.

Stand upright. Measure just below your breasts, keeping the tape level around your back. Do not pull to the point of pain.

The bra helps identify the lower edge of the breasts. Measure without a bra; keep the tape in the same place for all three readings, changing only the tension.

Same position · light contact

1. Loose underbust Let the tape just touch your skin, without digging in.

Same position · comfortably snug

2. Snug underbust Pull comfortably snug, as you would want a band to feel.

Same position · exhale, then tighten

3. Tight underbust Breathe out and pull the tape firmly, without causing pain.

About the calculation options

The ABTF manual developed its standard pathway for people assigned female at birth and its alternative weighting for people assigned male at birth. This is a method assumption, not a body assessment. Neither is validated for every body; choose the relevant pathway or use the quick estimate. This choice stays on your device.

Calculation pathway

Based on the ABTF community manual. Independently implemented, with our rounding and supported limits; results may differ from the ABTF online calculator. ABTF ↗

Optional local saving. The detailed record is separate from your quick measurements. Saving replaces the previous detailed record. Measurements are not uploaded or saved automatically.

03 / Fit guide

Know what a good fit feels like.

One sign alone cannot tell you which size to change. Check the whole bra and how it feels.

Band

Level and secure, without riding up or painful pressure.

If the band feels wrong

If the cups fit but the band rides up, compare a firmer band. Cups that are too small can also make the band feel tight.

Cups

Breast tissue stays inside, with a smooth edge rather than spilling or empty folds.

If there are gaps or spilling

Settle the tissue into the cups first. Cup size and shape can both cause problems; a gap alone does not mean you need a smaller cup.

Wires & straps

Wires sit around breast tissue. Straps stay in place without digging in.

Check the contact points

Wires should not rest on breast tissue. Many wired bras have a center bridge that lies against the chest; this is not a universal rule and does not apply the same way to wireless bras.

Fitting references: Bravissimo · ABTF

Same size, different cup shapes

Optional reading. These examples describe cup features to compare, not a way to add or subtract cup sizes.

More cup depth

If a cup feels too shallow, compare a deeper construction rather than assuming a bigger cup letter will solve it.

Cup-edge shape

An open or flexible upper edge may be worth comparing when the edge cuts in. Gaps can also reflect shape, not just size.

Uneven fullness

Check that the fuller side is comfortably contained. Stretch cup fabric may help accommodate the difference.

Wacoal ↗

Keep your quick measurements.

Save the two quick measurements separately from the detailed record, on this device only. Anyone using this browser may access them. Clearing browser data removes them.

Measurements are not saved automatically.

MEASURE WITH CONFIDENCE

How to measure your bra size

See where to place the tape, how snug to hold it, and how the quick and six-measurement methods differ.

Follow the illustrated measuring guide →

READ THE NUMBERS

Bra size chart

Look up starting bands and US/UK cup letters. Learn why a cup letter only makes sense together with its band.

Explore the band and cup chart →

UK bra size chart in inches and cm →

COMPARE LABELS

International bra size conversion

Already know your size? Compare US, UK, EU, French and Australian/New Zealand labels using our brand references.

Convert a bra size →

Bra size calculator FAQs

Can I use six measurements instead?

Yes. Open the optional detailed calculator for three underbust and three bust measurements, taken without a bra. It independently follows the ABTF community manual with documented product choices. More measurements do not guarantee a better fit; the detailed and quick methods use different measurement conditions.

How does this bra size calculator work?

Quick mode converts measurements to inches, rounds underbust to the nearest even band, rounds bust to a whole inch, then uses the difference for the cup step. Halfway values round up. The result is a starting size, not a fitting guarantee.

Can I calculate my bra size in centimeters?

Yes. Choose centimeters and enter your measurements directly. We use exactly 2.54 cm per inch. Switching units keeps the same underlying measurements.

Are US and UK bra sizes the same?

Many smaller cup labels match, but the sequences diverge after DD. For example, this calculator maps UK E to US DDD, and UK F to US G. Check the specific brand’s chart.

What is a sister size?

A sister size changes the band one step and the cup in the opposite direction to keep roughly similar capacity. For example, 34C has nearby sister sizes 32D and 36B. They can feel different.

How accurate is an online bra size calculator?

It can give you a useful starting point. Measurement technique, breast shape, bra construction and personal comfort affect fit. We do not claim a universal accuracy percentage or recommend a specific product.

Does gaping mean my cup is too big?

Not necessarily. Size, cup shape and how the bra is positioned can all contribute. Check the band and the whole cup before deciding to size down.

What if the calculator cannot give me a size?

This quick method supports underbust 26–50 inches and cup differences of 0–12 inches after rounding. Those are tool limits, not limits on normal bodies. Recheck the units and measurements, or use another fitting method.

Do you save or share my measurements?

Calculations run on your device. Measurements are saved only when you choose Save, and stay in this browser. They are not placed in URLs or sent to our server. There are no accounts or photo uploads.

Method reviewed: September 29, 2026 · Method & sources