Bra Cup Size Chart & Sister Sizes: The Complete 2026 US Sizing Guide

US Bra Size Chart (Band × Cup)

This is the complete US bra size chart used by virtually every US lingerie brand, including Irene's Secret. To use it, measure your band (under your bust) and your bust (at the fullest point), then find your size where the two meet.

Band Sizes 28–32

Band Sizes 34–40

Band Sizes 42–50 (Plus Size)

Tip: If you wear a DD cup or larger, the same rules apply — but most US brands use DDD instead of E or F. Always check the brand's specific size chart since naming conventions vary slightly.

How to Measure Your Bra Size (3 Steps)

You only need a soft measuring tape. Total time: under 5 minutes.

Step 1: Measure Your Band Size

1. Stand in front of a mirror, without a shirt (or in a non-padded bra).
2. Wrap the measuring tape snugly around your rib cage directly under your bust, where the band of a bra would sit.
3. Keep the tape level and parallel to the floor.
4. Exhale normally and record the number in inches.
5. Round to the nearest even number. (If you get 33", round to 34".)

Quick check: The tape should feel snug — you should be able to fit two fingers under it, but not your whole hand.

Step 2: Measure Your Bust

1. Wrap the measuring tape around the fullest part of your bust (usually across the nipple line).
2. Keep the tape level but don't pull it tight.
3. Record the number in inches.

Step 3: Calculate Your Cup Size

1. Subtract your band measurement from your bust measurement.
2. Use the table below to find your cup letter.

Example: Band = 34", Bust = 37" → 37 − 34 = 3" → You're a 34C.

Cup Size Table (AA → DDD → G)

The US cup progression: each cup letter represents a 1-inch difference between your bust and your band.

Note on naming: After D, US and UK systems diverge. The same cup volume may be called DD (US) or E (UK), or DDD (US) or F (UK). Always check the brand's specific chart.

Bra Sister Sizes: The Complete Chart

Bra sister sizes are alternative sizes that have the same cup volume but a different band and cup letter combination. The rule: for every 2-inch change in band, the cup letter changes by 1 (in the opposite direction) to maintain the same breast volume.

Why Sister Sizes Matter

• Your usual size is out of stock
• Your band runs tight or loose between brands
• You want a more comfortable fit without changing cup volume
• You're between sizes (common during weight changes)

Sister Sizes Chart (Most Common Sizes)

How to Use Sister Sizes

• Band feels tight? Go up a band size, down a cup letter (34C → 36B).
• Band feels loose? Go down a band size, up a cup letter (36D → 34DD).
• Straps digging in? Usually a sign the band is too loose — try going down a band.
• Cup spillage at the top? Go up a cup letter at the same band.

For a deeper dive into sister sizes, see our Sister Sizes: What They Are & How to Use Them guide.

International Bra Size Conversion (US / UK / EU / FR / AU)

Shopping from a non-US brand? Here's how the same size translates across the major sizing systems. The cup progression is similar; the band label changes by country.

Important: The cup letter starts to diverge after D. US DD = UK E, US DDD = UK F. EU/FR/AU/JP use the same letter system as UK. The band is the same letter/number but the actual measurement differs (US/UK use inches, EU/FR/JP use centimeters, AU/NZ use a number scale).

For a complete international conversion chart, see our International Bra Conversion Chart guide.

Best Bras by Size Range

Once you know your size, the next question is: which bra style is right for you? Here's a quick guide.

Small Busts (AA – B)

Small busts are demi bras and bralettes country. Demi cups give lift and shape without overwhelming, and bralettes offer wire-free comfort. Push-up styles work well if you want more cleavage on date nights.

Plunge Push-Up Bra with Removable Straps — a versatile demi/push-up that works under V-necks and t-shirts alike.

Average Busts (C – D)

The widest size range — most styles will work. Wireless bras are the most popular everyday pick for comfort; lace bras add elegance for special occasions; seamless bras disappear under t-shirts.

Seamless Wireless Bra & Thong Set — true to US sizing, smooth under everything, no underwire.

Full Busts (DD – DDD)

Full busts need full coverage cups, wider bands, and supportive straps. Wireless full-coverage bras are the most comfortable everyday option; underwire styles provide more lift but require a precise fit.

2-Pack Lace Deep-V Wireless Bra Set — wireless, full coverage, front closure for easy on/off.

Plus Size (40+ band)

Plus-size bras need extra reinforcement: wider bands, stronger elastic, and 3+ hook-and-eye closures. Look for brands that specialize in plus sizes and provide detailed fit guides.

The 4-Point Bra Fit Check

Even with perfect measurements, a bra can fit wrong. Walk through this checklist after you put one on:

1. Band: Sits level all the way around — never riding up your back. Two fingers should slide under the band, not your whole fist.
2. Straps: Doing about 20% of the work. If they're digging in or falling off, the band size is wrong.
3. Cups: No spillage at the top or sides. Wrinkles or gaps in the cup usually mean you need to go down a cup size.
4. Underwire (if any): Lays flat against your sternum and fully encases breast tissue. If it pokes your armpit, try a wider wire or a wireless style.

For a deeper fit walkthrough, see our How a Bra Should Fit guide.

Related Sizing & Bra Guides

Looking for a more specific topic? These guides go deeper on individual subjects covered above:

• How to Measure Bra Size (Step-by-Step)
• Understanding Bra Cup Sizes (Deep Dive)
• Bra Sister Sizes: What They Are & How to Use Them
• Sister Sizes: Finding Your Perfect Fit
• International Bra Conversion Chart
• Bra Size Calculator & Conversion
• How to Choose the Perfect Bra
• Choosing a Bra: A 6-Step Guide
• Bra Cup Sizes Explained
• How to Find Your Cup Size
• Understanding Breast Cup Sizes
• How a Bra Should Fit
• Demi vs Full Coverage Bra
• What Is a Demi Bra
• What Is a Contour Bra
• What Is a Bralette
• Sports Bra Sizing Guide

Frequently Asked Questions

What is the most common bra size in the US?

The most commonly sold bra size in the US is 36C, but the most commonly worn size is 34DD — because so many women are wearing the wrong band and don't know it. Studies show roughly 80% of women wear a bra that's the wrong size, usually with a band that's too big and a cup that's too small.

How accurate is a bra size chart?

Bra size charts are a starting point, not a final answer. Two women with identical measurements can prefer different sizes depending on breast shape, brand, and style. Always use the chart as a starting point and verify with the 4-point fit check.

What are bra sister sizes?

Bra sister sizes are alternative sizes with the same cup volume but different band and cup combinations. For example, 34C, 32D, and 36B are all sister sizes — they hold the same cup volume. You use them when your usual size is out of stock or doesn't fit right (band too tight, band too loose, etc.).

How do I find my bra sister size?

Use the sister size chart above. The rule: for every 2-inch increase in band, decrease the cup letter by 1. So 34C → 36B (band +2", cup −1) → 38A (band +2", cup −1). In the other direction, 34C → 32D → 30DD.

Do US and UK bra sizes use the same letters?

For bands and cups A through D, yes. After D, the systems diverge: US DD = UK E, US DDD = UK F, US DDDD = UK G. EU/FR/AU/JP use the UK system. The band is the same number but the unit differs — US/UK use inches, EU/FR/JP use centimeters.

What if I'm between two sizes?

Go with the larger cup. A bra that fits the larger breast always looks better than one that squishes the smaller one. If the bigger cup gapes on one side, look for a style with removable padding so you can even things out.

Do sports bras use the same sizing?

Not always. Compression sports bras are sized XS through 3XL. Encapsulation sports bras (with separate cups) are sized by band and cup. See our sports bra sizing guide.

How often should I re-measure?

Every 6 to 12 months, or after any weight change of 5+ pounds, a pregnancy, or a hormonal shift. Your rib cage and breast tissue both change over time.

What does DDD mean?

DDD is the US equivalent of UK F. It represents a 6-inch difference between your bust and band measurements. In EU/FR/AU/JP systems, the same volume is just called F.