How to Measure Your Bra Size at Home: A Complete Global Guide

It is a widely acknowledged fact in the apparel industry that a significant majority of women wear the wrong bra size at some point in their lives. Wearing the wrong size isn't just an aesthetic issue; it can lead to physical discomfort, back pain, shoulder indentations, and even posture problems. Fortunately, you don't need to visit a specialized lingerie boutique to find your true fit. With a simple measuring tape and a few minutes of your time, you can accurately calculate your bra size right at home.

In this comprehensive guide, we will walk you through the step-by-step process of measuring your underbust (ribcage) and your bust, explain what these numbers mean, and share the secret tips for getting the most accurate result. If you already have your measurements and want an instant result, you can jump straight to our Bra Size Calculator.

Preparation: What You Need for an Accurate Measurement

Before you begin, gather the following:

• A flexible measuring tape: Also known as a tailor's tape, this is essential as it can easily contour to the curves of your body. Do not use a stiff metal construction tape.
• A full-length or large mirror: Measuring in front of a mirror ensures that the tape remains parallel to the floor across your back, which is crucial for an accurate reading.

Pro Tip: For the best results, take your measurements either bare-chested or while wearing your best-fitting, unpadded everyday bra. Avoid wearing push-up bras or highly compressive sports bras, as these will artificially alter your bust volume and lead to a mathematically incorrect cup size calculation.

Step 1: Measuring Your Underbust (The Band Size)

The underbust measurement determines your band size (e.g., 34 in the US/UK, or 75 in the EU). The band is the foundation of a bra, providing up to 80% of the support. Therefore, getting this number right is the most critical part of the process.

The Measurement Technique

1. Wrap the measuring tape around your ribcage, directly underneath your breasts where the bra band would naturally sit.
2. Look in the mirror to ensure the tape is completely level and parallel to the floor all the way around your back. It shouldn't ride up or dip down.
3. Pull the tape so it sits snugly against your skin. It shouldn't be so tight that it restricts your breathing, but it shouldn't be loose either.
4. Exhale naturally (don't force all the air out of your lungs, just a normal breath out) and record the number in centimeters (cm).

Example Scenario: If your measurement is 73 cm, this is your raw underbust size. In the European (EU) sizing system, this number is typically rounded to the nearest multiple of 5 (which would be 75). In the US/UK system, this translates to a band size of 34.

Step 2: Measuring Your Bust (The Cup Size)

Your bust measurement, when compared to your band size, is what determines your cup letter (A, B, C, D, etc.).

The Measurement Technique

1. Wrap the tape around the fullest part of your breasts, which is typically right across the nipples.
2. Again, check the mirror to make sure the tape is parallel to the ground across your back.
3. Unlike the underbust measurement, the tape should rest lightly against your skin here. Do not pull it tight; it should not compress or squash your breast tissue at all.
4. Take a normal breath and record the number in centimeters (cm).

Example Scenario: If the tape reads 89 cm at the fullest part of your bust, record this value.

Step 3: Calculating Your Size from the Measurements

Now you have two crucial numbers. The math behind bra sizing works by using the underbust to set the band, and the difference between the bust and the band to determine the cup volume.

Finding the Band Size (EU Standard)

In the European system, the underbust measurement is rounded to the nearest 5 cm increment.

• If your underbust is 73 cm, it rounds up to 75.
• If your underbust is 71 cm, it rounds down to 70.

Finding the Cup Size

The cup size is determined by the formula:
Bust Measurement - Rounded Band = Difference

Based on this difference, the cup size is approximately assigned as follows:

• Difference ~ 10-12 cm: AA Cup
• Difference ~ 12-14 cm: A Cup
• Difference ~ 14-16 cm: B Cup (Considered an average volume)
• Difference ~ 16-18 cm: C Cup
• Difference ~ 18-20 cm: D Cup
• Difference ~ 20-22 cm: E Cup

Case Study: Let's look at Sarah's measurements.
Underbust: 76 cm
Bust: 92 cm

1. Band Rounding: 76 cm is closest to 75. Her band size is 75.
2. Calculate Difference: 92 (Bust) - 75 (Band) = 17 cm.
3. Determine Cup: A 17 cm difference falls squarely into the C Cup range (16-18 cm).
4. Final Result: Sarah's approximate EU bra size is 75C.

Doing this math manually every time you change weight or buy a new brand can be tedious. To get an instant and accurate result, simply input your numbers into our Bra Size Calculator. The calculator also allows you to adjust for a "Snug" or "Relaxed" fit, providing alternative sizes based on your personal comfort preferences.

Common Measuring Mistakes to Avoid

• Letting the tape slip in the back: This is the most common error when measuring without a mirror. If the tape drops in the back, the circumference increases, leading to a falsely large band size.
• Holding your breath: If you inhale deeply and hold your breath while measuring your bust, your ribcage expands, which can artificially inflate your cup size calculation. Always measure on a relaxed exhale.
• Measuring during hormonal fluctuations: Breasts can swell significantly right before or during your menstrual cycle. For the most baseline accurate reading, measure a few days after your cycle ends.

Final Thoughts

Measuring yourself at home is the best starting point for finding the perfect bra. Once you have your numbers and have used the calculator to find your starting size, you can shop with confidence. Keep in mind that just like jeans or shoes, every lingerie brand has slightly different cuts, fabrics, and fits. While the math might tell you that you are a 75C, you might find that in certain brands, an 80B (a sister size) feels much better. Let the calculator give you the map, but always let your personal comfort be the ultimate guide.