Bra Size Calculator
Find your perfect fit in seconds — accurate, private & free
📖 How to Measure Your Bra Size at Home
Getting an accurate bra size starts with two simple measurements. Follow these steps carefully for the best results. All you need is a soft measuring tape and a mirror (optional but helpful).
Measure Your Band (Underbust)
Wrap the measuring tape snugly around your ribcage, directly under your bust. Keep the tape parallel to the floor. Exhale gently and take the measurement. Round to the nearest whole number.
Measure Your Bust
Wrap the tape loosely around the fullest part of your bust (usually at nipple level). Keep the tape parallel to the floor. Don't compress — the tape should rest gently against your skin. Round to the nearest whole number.
🔢 Understanding Your Bra Size Results
A bra size consists of two parts: the band size (the number) and the cup size (the letter). For example, in "34C," 34 is the band size and C is the cup size.
- Band Size: This is your underbust measurement rounded to the nearest even number. It represents the circumference of your ribcage in inches.
- Cup Size: This is determined by the difference between your bust measurement and your band size. Each inch of difference corresponds to a cup letter (1" = A, 2" = B, 3" = C, etc.).
Our calculator uses the modern fitting method recommended by professional bra fitters — no arbitrary "add 4 inches" rule. This gives you a more accurate starting size.
🌍 International Bra Size Conversion Chart
Bra sizes vary between countries. Use the chart below to convert your size across different international sizing systems:
| US / UK Band | EU Band | FR / ES Band | AU / NZ Band | Cup (All) |
|---|---|---|---|---|
| 28 | 60 | 75 | 6 | A–K |
| 30 | 65 | 80 | 8 | A–K |
| 32 | 70 | 85 | 10 | A–K |
| 34 | 75 | 90 | 12 | A–K |
| 36 | 80 | 95 | 14 | A–K |
| 38 | 85 | 100 | 16 | A–K |
| 40 | 90 | 105 | 18 | A–K |
| 42 | 95 | 110 | 20 | A–K |
Note: Cup letters are generally consistent across all sizing systems through DD. Beyond DD, US and UK cup labeling differs (US uses DDD, G, H… while UK uses E, F, FF…). Our calculator accounts for these differences.
⚠️ Signs You're Wearing the Wrong Bra Size
Studies suggest that up to 80% of people wear the wrong bra size. Here are common telltale signs that your bra doesn't fit correctly:
- Straps dig into your shoulders — This often means the band isn't providing enough support, forcing the straps to carry too much weight.
- The band rides up your back — If the band curves upward between your shoulder blades, it's too loose. The band should sit level all the way around.
- Underwire pokes or floats — The underwire should sit flat against your ribcage, encasing your breast tissue without digging in or hovering away.
- Spillage or gaping cups — If breast tissue spills over the top or sides (quad-boob), the cup is too small. If there's empty space or wrinkling, the cup is too large.
- You fasten on the tightest hook — A new bra should fit comfortably on the loosest hook. As the elastic stretches over time, you can move to tighter hooks.
🙋 Frequently Asked Questions
How often should I measure my bra size?
It's recommended to measure your bra size every 6–12 months, or whenever you experience significant weight changes (gain or loss of 10+ lbs), pregnancy, breastfeeding, or hormonal changes. Your bra size can fluctuate more than you might think!
What is a "sister size" and should I use it?
A sister size is a bra size with the same cup volume but a different band size. For example, 34C has the same cup volume as 32D and 36B. Sister sizing is helpful when a particular brand's band runs tight or loose, but always start with your true measured size first.
Why does my bra size differ between brands?
Unfortunately, there is no universal standard for bra sizing. Different brands use different fit models and grading methods. A 34C from one brand might fit like a 32D from another. Always check the brand's specific size chart and read customer reviews about fit before purchasing.
Is the "add 4 inches" method still used?
The traditional "+4 method" (adding 4–5 inches to the underbust measurement) was developed when bras were made from non-stretchy materials like cotton and silk. Modern bras use elastic fabrics, so most professional fitters now recommend using your actual underbust measurement rounded to the nearest even number — which is what our calculator uses.
Can I measure my bra size without a measuring tape?
While a soft measuring tape gives the most accurate results, you can use a piece of string or ribbon in a pinch. Wrap it around your body, mark the meeting point, then measure the length against a ruler or yardstick. Just make sure the string doesn't stretch!
What if my bust is smaller than my underbust?
If your bust measurement is smaller than or equal to your underbust measurement, you may need an AA or AAA cup, or you might benefit from bralettes or alternative styles. Double-check your measurements — the bust should be measured at the fullest point. If the difference is still very small, look for brands that specialize in smaller cup sizes.
