How To Find My Bra Size Calculator

An accurate tool to find your bra size based on your body measurements.

Sister Size Chart

If your calculated size doesn’t feel quite right, you might fit better in a “sister size”. These are alternate sizes where the cup volume is the same. If you go up a band size, go down a cup size, and vice versa.

Go Down a Band Size (Tighter Band, Larger Cup)	Your Calculated Size	Go Up a Band Size (Looser Band, Smaller Cup)
—	—	—

Your sister sizes have the same cup volume as your calculated size.

What is a ‘how to find my bra size calculator’?

A ‘how to find my bra size calculator’ is a specialized tool designed to estimate your correct bra size based on two key body measurements: your underbust and bust circumference. Finding the right bra size is crucial for proper support, comfort, and posture. Studies show that a large percentage of women wear the wrong bra size, leading to issues like back pain, slipping straps, and general discomfort. This calculator helps demystify the process by applying a standard formula to your unique measurements.

The Bra Size Formula and Explanation

Bra sizing is a two-part system: the band size (a number) and the cup size (a letter). Our how to find my bra size calculator uses a common method to determine both.

Formula Steps:

1. Determine Band Size: Your raw underbust measurement is rounded to the nearest whole number. Then, if the number is even, 4 inches are added. If it’s odd, 5 inches are added. (Note: This “+4/+5” method is a traditional approach; some modern brands use the raw underbust measurement. This calculator uses the traditional method.)
2. Determine Cup Size: The calculated band size is subtracted from the bust measurement. The difference in inches corresponds to a cup letter.

Bra Size Calculation Variables

Variable	Meaning	Unit	Typical Range
Underbust Measurement	The circumference of the ribcage directly under the breasts.	in / cm	26 – 48 in
Bust Measurement	The circumference over the fullest part of the bust.	in / cm	30 – 55 in
Band-Bust Difference	Bust Measurement – Calculated Band Size. This determines the cup letter.	inches	0 – 12 in

Practical Examples

Example 1: Using Inches

• Inputs: Underbust = 31 inches, Bust = 37 inches.
• Band Calculation: 31 is odd, so 31 + 5 = 36. Your band size is 36.
• Cup Calculation: 37 (Bust) – 36 (Band) = 1 inch difference. A 1-inch difference is a ‘A’ cup.
• Result: 36A. (Note: other calculation methods may yield different results, for example 34C).

Example 2: Using Centimeters

• Inputs: Underbust = 80 cm, Bust = 95 cm.
• Conversion: 80cm is ~31.5 inches. 95cm is ~37.4 inches.
• Band Calculation: The calculator rounds 31.5 to 32. 32 is even, so 32 + 4 = 36. Your band size is 36.
• Cup Calculation: 37.4 (Bust) – 36 (Band) = 1.4 inch difference. A ~1 inch difference is an ‘A’ cup.
• Result: 36A.

How to Use This ‘how to find my bra size calculator’

Using the calculator is simple and takes just a few moments. For the most accurate results, it’s best to measure while wearing a non-padded, lightly-lined bra.

1. Select Your Units: Choose between ‘Inches (in)’ or ‘Centimeters (cm)’ from the dropdown menu.
2. Measure and Enter Underbust: Wrap a soft measuring tape snugly around your ribcage, directly under your bust. The tape should be level with the floor. Enter this number into the “Underbust Measurement” field.
3. Measure and Enter Bust: Wrap the tape around the fullest part of your bust. The tape should be comfortably loose and not compressing your chest. Enter this number into the “Bust Measurement” field.
4. View Your Results: The calculator will instantly update to show your estimated bra size, band size, cup letter, and sister sizes. The chart will also update to visualize your measurements.

Key Factors That Affect Bra Fit

Your calculated size is an excellent starting point, but several factors can influence the perfect fit:

• Brand & Style: Sizes can vary significantly between brands and even between different styles (e.g., plunge, full-cup, t-shirt bra) from the same brand.
• Breast Shape: Your breast shape (e.g., round, slender, teardrop) can affect how you fill out a cup. Some styles will suit your shape better than others.
• Band Snugness: The band provides most of the support. It should be snug but comfortable, and sit parallel to the floor without riding up.
• Cup Fit: There should be no gapping at the top of the cups or spillage over the top or sides (“quad-boob”). The center panel (gore) should lie flat against your sternum.
• Time of the Month: Hormonal fluctuations can cause breasts to swell, temporarily changing your size.
• Age and Weight Changes: Your bra size can change multiple times throughout your life due to age, pregnancy, weight loss, or weight gain. It’s a good idea to remeasure every 6-12 months.

Frequently Asked Questions (FAQ)

1. How do I measure myself correctly?

Stand straight with relaxed arms. Use a soft, flexible measuring tape. For the underbust, pull the tape snug. For the bust, keep the tape level but a bit looser.

2. What are sister sizes?

Sister sizes are alternate sizes with the same cup volume. For example, a 34C has the same cup volume as a 32D and a 36B. They are useful if a bra fits in the cup but not the band.

3. What if I’m between sizes?

If you’re between sizes, sister sizing is your best tool. Also, consider your breast shape and the brand you’re buying. Trying both potential sizes is recommended.

4. Why does my band ride up in the back?

This is a classic sign that your band is too big. The band should provide about 80% of the support. Try a smaller band size (and likely a larger cup size to maintain volume, i.e., a sister size).

5. What does “spillage” or “quad-boob” mean?

This happens when your cup size is too small, causing your breast tissue to spill over the top of the cup. You should go up one or more cup sizes.

6. Is the “+4/+5 inch” band method always accurate?

No, it’s a traditional method that works for many but not all. Some modern brands and fitters now recommend using your raw underbust measurement as your band size. If our calculator’s suggestion feels too loose in the band, try a size based on your raw measurement.

7. Why does the center panel (gore) not touch my chest?

This usually indicates the cups are too small. Your breasts are pushing the bra away from your body. Try going up a cup size.

8. What if one breast is larger than the other?

This is very common. Always fit to the larger breast to avoid spillage. You can use a small pad or “cookie” in the cup of the smaller breast to create a symmetrical look.