Maternity Bra Size Calculator
Use our free bra size calculator to find your perfect fit. Enter your measurements and get instant results in US, UK, EU, and 7+ international sizing systems.
Your data is never stored or shared. All calculations happen in your browser.
Enter your measurements to see your bra size results here
Results include US, UK, EU, FR, IT, AU, and JP sizes
How to Use Our Bra Size Calculator
Finding the right bra size starts with accurate measurements. Our bra size calculator uses your underbust and bust measurements to determine your perfect fit across multiple international sizing systems.
Step 1: Gather Your Tools
You'll need a soft, flexible measuring tape. If you don't have one, you can use a string and then measure it against a ruler. Wear a non-padded bra or no bra for the most accurate results.
Step 2: Measure Your Underbust (Band Size)
Stand up straight and wrap the measuring tape around your ribcage, directly under your breasts. The tape should be snug but not tight — you should be able to fit one finger underneath. This measurement determines your band size.
Step 3: Measure Your Bust
Wrap the measuring tape around the fullest part of your bust. Keep the tape parallel to the floor and don't compress your breast tissue. For the most accurate result, we recommend also measuring while leaning forward at 90° (available in Advanced mode).
Step 4: Get Your Results
Enter your measurements into the calculator above and click "Calculate My Bra Size." You'll receive your recommended size in US, UK, EU, French, Italian, Australian, and Japanese sizing systems, along with sister size recommendations.
Understanding Your Bra Size Calculator Results
Your bra size consists of two components:
- Band Size (the number): This is based on your underbust measurement and indicates the circumference of the band. In US sizing, it's measured in even inches (32, 34, 36, etc.).
- Cup Size (the letter): This is determined by the difference between your bust and band measurements. Each inch of difference generally equals one cup size (1" = A, 2" = B, 3" = C, etc.).
Standard vs. Advanced Calculator Mode
Our standard mode requires just two measurements (underbust and bust) and is perfect for most users. The advanced mode uses four measurements for increased accuracy, especially helpful for those with softer or more projected breast tissue.
Why Use Our Bra Size Calculator?
- Instant results in 7+ international sizing systems
- Sister size recommendations included
- Advanced mode with 4 measurements for better accuracy
- Supports both inches and centimeters
- 100% free — no registration required
- Privacy-first: all calculations happen in your browser