VS Bra Calculator
Find your accurate bra size quickly and easily. Follow the steps below for a perfect fit.
Measure snugly around your ribcage, just beneath your bust.
Measure loosely around the fullest part of your bust.
What is a VS Bra Calculator?
A vs bra calculator is a specialized tool designed to help you determine your most accurate bra size based on two key body measurements: your band (underbust) and bust circumference. Unlike guessing or using outdated sizing methods, this calculator uses a standardized formula to translate your unique measurements into a specific band and cup size. The goal is to move beyond the high percentage of women wearing the wrong size and find a bra that offers optimal support, comfort, and confidence. This tool is for anyone who has experienced straps digging in, bands riding up, or cups gaping, providing a reliable starting point for your next lingerie purchase.
VS Bra Calculator Formula and Explanation
The calculation for finding your bra size is a two-step process. First, we determine your band size from your underbust measurement. Second, we find your cup size by calculating the difference between your bust measurement and your *newly calculated band size*.
- Band Size Calculation: Your underbust measurement is rounded up to the next nearest even number. This becomes your final band size.
- Cup Size Calculation: Cup Difference = Bust Measurement – Band Size.
The resulting difference in inches corresponds to a letter for your cup size. See our bra size chart for a full conversion.
| Variable | Meaning | Unit (Auto-Inferred) | Typical Range |
|---|---|---|---|
| Underbust Measurement | The measurement around your ribcage, just below the breasts. | Inches or cm | 26 – 48 in / 66 – 122 cm |
| Bust Measurement | The measurement around the fullest part of your bust. | Inches or cm | 30 – 55 in / 76 – 140 cm |
| Cup Difference | The result of subtracting the band size from the bust measurement. | Inches | 0 – 10+ in |
Understanding Sister Sizes
Your perfect fit might not be the exact size you calculate. This is where sister sizes come in. A sister size refers to an equivalent cup volume on a different band size. The rule is simple: if you go up one band size, you go down one cup size, and vice versa. For example, if our vs bra calculator gives you a 34C, your sister sizes are 32D (one band size down, one cup size up) and 36B (one band size up, one cup size down). Knowing this can be a game-changer when a bra almost fits perfectly.
| Go Down a Band (Tighter Band) | Your Calculated Size | Go Up a Band (Looser Band) |
|---|---|---|
| — | — | — |
Practical Examples
Example 1: Average Measurements
- Inputs: Band (Underbust) = 31 inches, Bust = 37 inches
- Band Size Calculation: 31 inches is rounded up to the next even number, which is 32.
- Cup Size Calculation: 37″ (Bust) – 32″ (Band Size) = 5″ difference.
- Results: A 5″ difference corresponds to a DD cup. The final size is 32DD.
Example 2: Using Centimeters
- Inputs: Band (Underbust) = 80 cm, Bust = 95 cm
- Unit Conversion: 80 cm ≈ 31.5 inches; 95 cm ≈ 37.4 inches.
- Band Size Calculation: 31.5 inches is rounded up to the next even number, which is 32.
- Cup Size Calculation: 37.4″ (Bust) – 32″ (Band Size) = 5.4″ difference.
- Results: A 5.4″ difference is closest to a DD/E cup. The final size is 32DD or 32E. Find out more with our sister size calculator.
How to Use This VS Bra Calculator
- Select Your Unit: Start by choosing whether you will measure in Inches or Centimeters.
- Measure Your Band: Wrap a soft measuring tape snugly around your ribcage, directly underneath your breasts. Ensure the tape is level all the way around. Enter this number into the “Band Measurement” field.
- Measure Your Bust: Now, wrap the tape around the fullest part of your bust. The tape should be level and not too tight. Enter this value into the “Bust Measurement” field.
- Review Your Results: The calculator will instantly display your calculated bra size, along with intermediate values like your band and cup size. It will also show you your sister sizes, which are crucial for finding the best fit.
- Interpret the Results: Use the calculated size as your starting point when shopping. Remember to try on the sister sizes as well to see which provides the most comfort and support.
Key Factors That Affect Bra Size
- Brand Differences: Sizing is not standardized across all brands. A 34C in one brand might fit differently than in another.
- Bra Style: A balconette, full-cup, or push-up bra will all fit differently due to their construction, even in the same size. A detailed bra fitting guide can help.
- Weight Fluctuation: Changes in body weight directly impact both your band and bust measurements.
- Hormonal Changes: The menstrual cycle, pregnancy, and menopause can all cause breast size to fluctuate.
- Time and Age: Over time, skin elasticity and breast tissue density change, which can alter your required size and support level.
- Measurement Accuracy: How you measure is critical. A tape that is too tight, too loose, or not level can lead to incorrect results.
Frequently Asked Questions
It’s recommended to measure yourself every 6-12 months or after any significant body changes (like weight loss/gain or pregnancy).
Many people are surprised by their calculated size. Cup sizes extend far beyond D (e.g., E, F, G, H). If the calculator gives you a 32G, it means your bust is 7 inches larger than your 32-inch band.
This is an outdated method that often results in a band that is too large and a cup that is too small. Modern methods, like the one used by this vs bra calculator, provide a more accurate and supportive fit by using a measurement closer to your actual ribcage size.
This is where sister sizing is essential! If a 34C cup fits well but the band is tight, try your sister size up: 36B. If the 34C band is good but the cup is a bit small, try a 34D. See our guide on Victoria’s Secret sizing.
While this calculator provides a great starting point, sports bras often use different sizing (S, M, L). However, knowing your precise bra size helps you choose a more accurate sports bra size from a brand’s specific chart.
Double-check that your measuring tape was level and snug (not tight) for the band measurement, and level and loose for the bust measurement. Also, ensure you are not wearing a padded or push-up bra while measuring.
The band provides about 80% of a bra’s support. A snug, correct-fitting band is the most critical element of a good fit. If the band rides up your back, it’s too big.
They look different, but they are designed to hold the same volume of breast tissue. A 32D has a deeper cup on a smaller frame, while a 36B has a shallower cup on a larger frame. Learn more about bra cup sizes.