Enter your measurements to find your perfect bra size…
Bra Size Calculator (US/UK, EU, AU). Uses underbust + overbust to calculate band & cup. Includes sister sizes, fit tweaks, and visual chart. Real-time, step-by-step, accurate to 0.5″.
Finding the perfect bra size can be challenging, but the right fit makes all the difference in comfort, confidence, and posture. A Bra Size Calculator is a simple yet accurate online tool designed to help you determine your correct bra size based on your measurements.
Whether you’re shopping online, experiencing discomfort with your current bras, or simply unsure about your true size, this calculator takes the guesswork out of the equation and helps you find the most comfortable, supportive fit for your body.
A Bra Size Calculator is an online tool that helps you find your correct bra size by using two key measurements: your band size and your bust size. It’s ideal for anyone who wants to make sure their bras provide the right support and shape — whether you’re a teenager buying your first bra, a new mom, or someone whose body has changed over time.
Most calculators follow the same basic method:
Measure around your ribcage (underbust) to find your band size.
Measure around the fullest part of your bust to determine your cup size.
The calculator uses these numbers to give your final bra size — such as 34B, 36C, or 38D.
A bra size calculator is a specialized tool that determines optimal bra size by analyzing two key measurements: under bust (band size) and bust (cup size). It converts these measurements into standardized sizing systems (like US/UK/EU) while accounting for variations in breast shape and body type. The concept of bra sizing originated in the 1930s when Warner Brothers introduced the A-D cup system, though modern calculators emerged with digital technology in the 2000s.
A Bra Size Calculator simplifies the sizing process into three easy steps:
Measure Your Band Size (Underbust):
Wrap a measuring tape around your ribcage, just under your bust. Round to the nearest whole number. If the number is even, add 4 inches; if it’s odd, add 5 inches — this gives your band size.
Measure Your Bust Size (Overbust):
Measure around the fullest part of your bust, keeping the tape parallel to the floor and not too tight or loose.
Calculate Cup Size:
Subtract your band measurement from your bust measurement. Each inch of difference equals one cup size:
The calculator then combines these measurements to produce your perfect bra size — for example, if your band size is 34 and the difference is 3 inches, your size is 34C.
Bra size calculators operate on anthropometric principles, translating body measurements into standardized sizing systems. The fundamental approach calculates band size based on underbust measurement and determines cup size by comparing bust to band measurements.
The core formulas are:
Cup Size Calculation:
The difference determines cup letter:
Step-by-Step Example 1: Standard Calculation Measurements:
Step 1: Calculate band size (US system) Band Size = 31 + 5 = 36 inches
Step 2: Calculate cup difference Cup Difference = 37 – 36 = 1 inch
Step 3: Determine cup size 1 inch = A cup
Result: 36A
To visualize sizing relationships, a table might show sister sizes (equivalent fits):
To use the calculator, you’ll need two measurements using a flexible measuring tape:
Band Size (Under bust):
Measure around your ribcage, directly under your bust. Keep the tape snug and level.
Bust Size (Over bust):
Measure around the fullest part of your bust. Don’t pull the tape too tight.
Bra size calculators serve critical functions across various scenarios, making them indispensable tools for women’s health and retail. Here are three key use cases where precise sizing is essential:
Postural Pain Management: For women experiencing chronic back/shoulder pain, proper bra support is often the first-line solution. Dr. Lisa Chen, Physical Therapist at Mayo Clinic, notes, “We see patients weekly with bra-related pain—deep shoulder grooves from straps, upper back strain from inadequate support. Our bra calculator helps identify correct sizing, and we’ve documented 70% pain reduction within 3 weeks of proper fitting.” A 2023 study in Journal of Women’s Health Physical Therapy found that women using calculator-guided sizing reported 65% fewer headaches and 58% less neck pain compared to those self-selecting sizes.
Here is how the difference translates into cup sizes globally:
| Bust – Band Difference | US Cup | UK/AU Cup | EU Cup |
|---|---|---|---|
| <1 inch | AA | AA | AA |
| 1 inch | A | A | A |
| 2 inches | B | B | B |
| 3 inches | C | C | C |
| 4 inches | D | D | D |
| 5 inches | DD or E | DD | E |
| 6 inches | DDD or F | E | F |
| 7 inches | G | F | G |
| 8 inches | H | FF | H |
| 9 inches | I | G | I |
| 10 inches | J | GG | J |
Note: Slight variation exists across brands and regions.
To simplify the sizing differences around the world, here’s a comparison of band sizes in different regional standards:
| Label | FR/ES | EU | US/UK | AU/NZ |
|---|---|---|---|---|
| XS | 80 | 65 | 30 | 8 |
| S | 85 | 70 | 32 | 10 |
| M | 90 | 75 | 34 | 12 |
| L | 95 | 80 | 36 | 14 |
| XL | 100 | 85 | 38 | 16 |
| XXL | 105 | 90 | 40 | 18 |
| 3XL | 110 | 95 | 42 | 20 |
| 4XL | 115 | 100 | 44 | 22 |
Finding the perfect bra size shouldn’t be a guessing game. With a proper bra size calculator, global size charts, and awareness of the signs of a poor fit, you can finally wear bras that provide true comfort and support. Remember, sizes are just a guideline—how the bra feels is what truly matters.
A Bra Size Calculator is one of the simplest yet most empowering tools for women. It helps you discover your perfect size quickly, ensuring comfort, confidence, and the right level of support every day.
Your bra shouldn’t pinch, gap, or feel uncomfortable — it should make you feel supported and natural. Whether you’re buying your first bra, updating your wardrobe, or adjusting after body changes, the Bra Size Calculator is your go-to guide for finding your perfect fit. Measure, calculate, and wear your confidence every day — because the right fit changes everything!
A Bra Size Calculator is an online tool that helps you determine your correct bra size using two key measurements — your band (underbust) and bust (overbust). It instantly calculates your cup size and final bra size, such as 34B or 36C, ensuring a perfect, comfortable fit.
To measure correctly:
Wrap a measuring tape around your ribcage (under your bust) for the band size.
Then, measure around the fullest part of your bust.
Subtract the band measurement from the bust measurement — each inch of difference equals one cup size (1″ = A, 2″ = B, 3″ = C, etc.).
The calculator then combines these to give your accurate bra size.
You should measure yourself every 6 to 12 months, or sooner if you’ve experienced weight changes, pregnancy, breastfeeding, or discomfort with your current bras. Body shape and size can change naturally over time.
You may be wearing the wrong bra size if:
The straps dig into your shoulders or keep slipping.
The underwire pokes or feels tight.
The cups gap, wrinkle, or overflow.
The band rides up your back.
Using a Bra Size Calculator helps fix these fit issues immediately.
Yes. Sizing can vary slightly between brands and countries. Once you know your true size from a Bra Size Calculator, use each brand’s conversion chart to find the best fit for their specific sizing system.
Absolutely. An ill-fitting bra can cause poor posture, shoulder and back pain, and skin irritation. The right size provides balance and support, improving both comfort and confidence.
Band size measures the area directly under your bust and forms the base of the bra.
Cup size measures the fullness of your bust and determines how much coverage and support you need.
Together, they create your complete bra size — for example, 36C or 32B.
For best results:
Use a soft measuring tape.
Stand in front of a mirror to ensure the tape is level.
Wear a lightly padded or non-padded bra.
Take measurements in inches (or centimeters, depending on the calculator).
Yes! Factors like weight changes, aging, hormones, pregnancy, and even exercise can affect your size and shape. That’s why it’s important to recalculate regularly using a Bra Size Calculator.
If you fall between sizes, try sister sizing. For example, if 34C feels tight in the band, try 36B — the cup volume stays similar but the band fits looser. The calculator can help guide you toward the most comfortable option.