Accurate Bra Size Calculator
Find your perfect fit in seconds with our free online bra size calculator. Enter your underbust and overbust measurements to calculate your band size, cup size, sister sizes, and international conversions.
Interactive Bra Size Calculator
Enter your underbust and overbust measurements below in our interactive bra size calculator to find your perfect fit. This tool supports both metric and imperial units, offering accurate size recommendations and regional conversions.
Your Recommended Bra Sizes
Based on your measurements from our bra size calculator, here are your recommended sizes across different regional standards:
Sister sizes share the exact same cup volume but have different band sizes. If your current bra band feels too loose (rides up your back), try sizing down in the band and up in the cup (e.g., from 34C to 32D). If the band feels too tight or digs in, try sizing up in the band and down in the cup (e.g., from 34C to 36B). This maintains the same cup capacity while adjusting band comfort.
“Hello neighbor! Sizing can be tricky, but this bra size calculator makes it smooth and easy! Make sure you measure flat against your skin while breathing naturally. Let's find your size below!”
Bra Size Chart & Regional Conversions
Compare international band and cup sizes with this reference chart alongside our bra size calculator:
| Underbust Range | US / UK Band | EU / JP / CN | FR / ES Band | AU / NZ Band |
|---|---|---|---|---|
| 23.6 - 25.6 in (60 - 65 cm) | 30 | 65 | 80 | 8 |
| 25.6 - 27.6 in (65 - 70 cm) | 32 | 70 | 85 | 10 |
| 27.6 - 29.5 in (70 - 75 cm) | 34 | 75 | 90 | 12 |
| 29.5 - 31.5 in (75 - 80 cm) | 36 | 80 | 95 | 14 |
| 31.5 - 33.5 in (80 - 85 cm) | 38 | 85 | 100 | 16 |
| 33.5 - 35.4 in (85 - 90 cm) | 40 | 90 | 105 | 18 |
| 35.4 - 37.4 in (90 - 95 cm) | 42 | 95 | 110 | 20 |
No Measuring Tape? How to Measure with Household Items
If you don't have a flexible measuring tape, you can use a piece of non-elastic string, ribbon, or even a shoelace. Wrap it around your chest, mark the overlap point, and compare the length against these common household items:
- Standard Credit Card: The longer border is exactly 3.37 inches (8.56 cm).
- US Dollar Bill: Standard US banknotes measure precisely 6.14 inches (15.6 cm) wide.
- A4 Printing Paper: The length of the page is 11.69 inches (29.7 cm), and the width is 8.27 inches (21.0 cm).
Sum up the lengths of these items to calculate your measurements, then enter them into the bra size calculator above.
Why Did Traditional Bra Fitting Use the "+4 Rule"?
Many older bra calculators and brand sizing guides still instruct you to add 4 or 5 inches to your underbust measurement. This "+4 rule" dates back to the 1930s, when bras were made of rigid, inelastic materials like cotton canvas and linen. To allow women to breathe and move comfortably, manufacturers had to artificially add 4 to 5 inches to the actual underbust measurement.
Today, modern lingerie is made with advanced elastic fibers like Spandex and elastane. Bra bands are designed to stretch and grip the ribcage comfortably. Adding 4 inches to your measurement today results in a band that is far too loose, causing it to slide up your back and placing all the support weight onto your shoulder straps. Our calculator defaults to a snug-band formula, providing correct, healthy support from the ribcage.
Why Do Actual Bra Sizes Differ from Calculator Estimates?
While our calculator provides a highly accurate starting point, actual sizes can vary between brands. Different manufacturers design their patterns around unique fit models, silhouettes, and fabric elasticities. Additionally, individual factors like breast shape (projected, shallow, asymmetric) and tissue firmness affect how a bra fits. We recommend using your calculated size as a baseline, checking brand-specific size guides, and trying sister sizes to find your perfect fit.
How to Measure Your Bra Size Accurately
For the most accurate calculation, grab a soft measuring tape and follow these two steps:
Step 1: Measure Your Underbust (Determines Band Size)
Stand up straight and breathe out comfortably. Place a soft measuring tape snugly around your ribcage, directly beneath your breasts where the bra band sits. Make sure the tape is parallel to the ground.
Step 2: Measure Your Overbust (Determines Cup Size)
Wrap the measuring tape loosely around the fullest part of your breasts, keeping the tape parallel to the floor. Do not pull it tight. Keep your arms relaxed at your sides.
Bra Size Calculator & Sizing FAQ
Answers to common questions about bra measurements, sizing formulas, and finding the perfect fit.