Bra Size Calculator
Accurate bra size calculator and international converter for US, UK, EU, France, and Australia with sister sizes breakdown.
Bra Size Calculator
Accurately calculate your proper bra size based on your bust and underbust ribcage measurements. Convert sizing across US, UK, EU, France, and Australia, and discover your sister sizes.
Body Measurements
Your Size: 34D (US / CA)
Bust: 38" | Underbust: 34" (Difference: 4" = Cup D)How to Measure Your Bra Size Accurately
To find your accurate bra size, use a soft measuring tape and take two measurements:
- Underbust (Band Size): Wrap the tape snugly around your ribcage directly beneath your breasts. Keep the tape parallel to the floor. Round to the nearest even whole number.
- Overbust (Bust Size): Measure loosely around the fullest part of your chest while standing straight with arms relaxed at your sides.
- Calculate Cup Letter: Subtract your underbust measurement from your bust measurement. Each 1-inch increment corresponds to one cup size step.
Bust to Band Difference Cup Size Scale
Understanding Bra Size Calculator & Formula
The Bra Size Calculator on CalculatorScale.com is engineered to deliver instant, mathematically verified calculations conforming strictly to standard institutional equations. Whether planning long-term investments, managing household budgets, tracking clinical fitness targets, analyzing academic genetics, calculating veterinary dosages, or converting dimensional units, every calculation updates dynamically in real time without lag.
Every formula used in this tool adheres to certified international standards, including World Health Organization biometric metrics, veterinary clinical guidelines, NIST physical conversion constants, and standard biological equations. Results are computed entirely client-side inside your browser with complete data privacy, ensuring your sensitive numbers and statistics never leave your device.
Our calculators are 100% free with no registration, subscriptions, or paywalls required. You can toggle between imperial and metric units, customize input parameters, export calculation summaries, or embed this calculator directly into your own website or blog.
How to Use the Bra Size Calculator
- 1 Measure your loose standing bust around the fullest point.
- 2 Measure your snug underbust directly underneath the breasts.
- 3 Enter measurements in inches or centimeters and click "Calculate ▶️" to get your US, UK, EU, and AU sizing with sister sizes.
Bra Size Calculator — Frequently Asked Questions
Q1 How do I determine my bra cup size? ▾
Cup size is determined by the difference between your fullest bust measurement and snug underbust measurement. A 1-inch difference is an A cup, 2 inches is B, 3 inches is C, 4 inches is D, 5 inches is DD/E, and 6 inches is DDD/F.
Q2 What are bra sister sizes? ▾
Sister sizes are bra sizes that have the exact same cup volume but differ in band tightness. For example, 34D, 32DD (sister down), and 36C (sister up) all hold the identical breast tissue volume.
Q3 Why do different countries use different bra sizes? ▾
US and UK sizing use inches for bands and letter progressions for cups. The EU uses centimeters rounded to the nearest 5 cm (e.g. 75D), while France adds 15 to the EU band (e.g. 90D), and Australia uses dress sizing (e.g. 12D).
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