What is a Bra Size?

Bra size is a combination of two measurements: your band size (under your bust) and your cup size (around the fullest part of your bust). Knowing your correct bra size is essential for both comfort and support. A properly fitting bra can make a huge difference in how your clothes fit and how you feel throughout the day.

How to Measure for a Bra Size

To find your correct bra size, you’ll need two measurements:

Once you have these two measurements, the calculator will help you determine your bra size, including your band and cup sizes. You can also check your "sister sizes"—which are different combinations of band and cup sizes that will give you a similar fit. If you're unsure, try a few sizes to see what feels best for you.

How Does the Bra Size Calculator Work?

Our Bra Size Calculator uses the following steps to find your perfect fit:

1. Band Size = Round your under-bust measurement to the nearest even number.
2. Cup Size = Difference between your bust measurement and your band size, which determines the cup letter.

Formula for Calculating Bra Size:

The formula for calculating bra size is simple:

Band Size = Round under-bust measurement (in inches or cm) to the nearest even number.

Once you have the band size, you calculate the cup size by finding the difference between your bust measurement (over the fullest part of your bust) and your band size. The larger the difference, the larger the cup size. The cup sizes follow this scale:

Example: If your under-bust measurement is 32 inches, your band size is 32 (since it’s already an even number). If your bust measurement is 36 inches, the difference between your bust and band is 4 inches, which would give you a "D" cup size. So, your bra size would be 32D.

The calculator uses these formulas to quickly determine your bra size and even provides you with possible sister sizes, which are alternative sizes that offer a similar fit. Sister sizes are particularly useful if a certain size feels too tight or too loose. They allow you to try a different combination of band and cup size while maintaining a similar cup volume.

What Are Sister Sizes?

Sister sizes are alternate bra sizes that have the same cup volume but different band measurements. If you find that a particular bra isn't fitting quite right, you can try a sister size for a better fit. The calculator will provide you with sister sizes based on your measurements.

5 FAQs for Better Understanding

1. How do I know if my bra size is correct?

Your bra should feel snug but comfortable around the band, and the cups should fully support your bust without causing bulging or gaping. If the band rides up in the back or if the straps dig into your shoulders, you might need a different size.

2. What if I have a different band size in one brand?

Different brands may fit differently due to their sizing standards. Always try on a bra before buying, especially when switching brands. Our calculator gives you an estimate, but the best way to know your size is to try it on!

3. Can I use this calculator for sports bras or maternity bras?

This calculator is designed for everyday bras. For sports bras, you may need to choose a size based on your activity level and the level of support you need. Maternity bras may also require different sizing depending on changes in your body during pregnancy.

4. What if my measurements fall between sizes?

If your measurements fall between two sizes, we recommend trying both to see which one feels more comfortable. In many cases, choosing a larger cup size and a smaller band size (or vice versa) might give you the best fit.

5. Can I change the measurement system from inches to centimeters?

Yes! Our calculator allows you to switch between inches and centimeters, depending on which unit you're more comfortable with. Just select your preferred system, and the calculator will adjust accordingly.