Find Perfect Bra Size Calculator

Bra Size Calculator

Enter your measurements to find your estimated bra size. For best results, measure without a bra or with a non-padded, non-wired bra.

What is a Bra Size Calculator?

A bra size calculator is a tool designed to estimate a person's bra size based on their body measurements, specifically the underbust (band) and bust circumference. It uses these measurements to suggest a band size and cup size. While not a definitive final answer, as bra fit varies by brand and style, a bra size calculator provides an excellent starting point for finding a comfortable and supportive bra.

Anyone who wears a bra and is unsure of their current size, or suspects their size has changed, should use a bra size calculator. This is particularly useful after weight fluctuations, pregnancy, or simply if it's been a while since the last measurement.

Common misconceptions include believing bra sizes are static throughout life or that all brands fit the same. A bra size calculator helps address these by providing a current estimate, but it's always recommended to try bras on to confirm the fit.

Bra Size Calculator Formula and Mathematical Explanation

The calculation for bra size involves two main components: the band size and the cup size.

1. Band Size Determination:
   • Measure snugly around the ribcage, just under the bust (Underbust Measurement).
   • Round the measurement to the nearest whole number.
   • If the rounded number is odd, add 1 to get the band size (e.g., 29 inches becomes 30). If it's even, the band size is that number (e.g., 30 inches is 30). Some calculators or methods might add 4 or 5 inches to the raw underbust, but the method described (round, then add 1 if odd) is more common for modern fitting and used here.
2. Cup Size Determination:
   • Measure around the fullest part of the bust (Bust Measurement).
   • Subtract the calculated Band Size number from the Bust Measurement. The difference in inches determines the cup size.
   • Difference (inches): 0-1=AA, 1=A, 2=B, 3=C, 4=D, 5=DD/E, 6=DDD/F, 7=G, 8=H, 9=I, 10=J, 11=K, 12=L (US Sizing).

So, Bra Size = Band Size + Cup Letter (e.g., 34C).

Variables Table:

Variable	Meaning	Unit	Typical Range
Underbust Measurement	Circumference under the bust	inches or cm	26-50 inches (65-127 cm)
Bust Measurement	Circumference at the fullest part of the bust	inches or cm	28-60 inches (71-152 cm)
Band Size	The number part of the bra size	n/a (based on inches)	28, 30, 32, 34, 36, … 52
Bust-Band Difference	Bust Measurement – Band Size	inches	0 – 12+
Cup Letter	The letter part of the bra size	n/a	AA, A, B, C, D, DD, DDD/F, G…

Table showing variables used in the bra size calculator.

Practical Examples (Real-World Use Cases)

Example 1:

• Underbust Measurement: 29.5 inches
• Bust Measurement: 35 inches
• Unit: inches

Calculation: Rounded Underbust = 30 inches. Band size = 30. Difference = 35 – 30 = 5 inches. Cup size = DD/E. Estimated Bra Size: 30DD (US) or 30E (UK).

Example 2:

• Underbust Measurement: 83 cm
• Bust Measurement: 99 cm
• Unit: cm

Conversion: Underbust = 83 / 2.54 ≈ 32.68 inches, Bust = 99 / 2.54 ≈ 38.98 inches. Rounded Underbust = 33 inches. Band size = 34. Difference = 38.98 – 34 ≈ 4.98 inches (around 5 inches). Cup size = DD/E. Estimated Bra Size: 34DD (US) or 34E (UK), or European 75E.

How to Use This Bra Size Calculator

1. Measure Yourself: Using a soft measuring tape, measure your underbust and bust circumference as described in the helper text. Keep the tape level and snug but not tight.
2. Enter Measurements: Input your underbust and bust measurements into the respective fields.
3. Select Unit: Choose whether you measured in inches or centimeters.
4. Calculate: The calculator will automatically update, or you can click "Calculate Size".
5. Read Results: Note your estimated band size, cup size, and full bra size. Also, look at the sister sizes provided.
6. Try On Bras: Use the calculated size as a starting point when shopping. Try on the suggested size, as well as the sister sizes, to see what fits best. Pay attention to the band, cups, and straps for a good fit. Learn more about bra fitting.

Key Factors That Affect Bra Size Results

• Measurement Technique: How snugly you pull the tape and whether it's level can alter readings.
• Bra Style and Brand: Different bra styles (e.g., plunge, full cup, balcony) and brands fit differently even in the same size. A bra size calculator gives a baseline.
• Body Changes: Weight fluctuations, hormonal changes, pregnancy, and aging can all affect breast size and shape, requiring a new measurement.
• Posture: Standing up straight while measuring is important for accuracy.
• Breast Shape: The shape of your breasts (e.g., round, shallow, projected) can influence which bra styles fit best, even if the size is correct.
• Band Snugness Preference: Some prefer a very snug band, others slightly looser, which might mean adjusting the band size from the calculator's result. Our bra style guide can help.
• Time of the Month: Breast size can fluctuate during the menstrual cycle.
• Manufacturing Variations: There can be slight differences between bras of the same size even from the same brand.

Frequently Asked Questions (FAQ)

1. How often should I use a bra size calculator?

It's a good idea to remeasure and use a bra size calculator every 6-12 months, or after significant body changes.

2. What if my measurements are between sizes?

Try the nearest sizes and sister sizes. Fit preference also plays a role. The bra size calculator gives a starting point.

3. What are sister sizes?

Sister sizes are bra sizes that have the same cup volume but different band and cup letter combinations. For example, 34C, 32D, and 36B are sister sizes. If your band is too loose in a 34C, try a 32D.

4. Does the calculator work for all countries (US, UK, EU)?

This calculator primarily uses US cup sizing progression (A, B, C, D, DD, DDD/F, G…). UK and EU sizing can differ, especially in larger cup sizes. We provide a basic idea and our international size chart can help convert.

5. Why does my calculated size seem wrong?

The bra size calculator provides an estimate. Brand variations, bra style, and individual body shape mean the best fit might be slightly different. Always try bras on.

6. Should the measuring tape be tight or loose?

Snug but not digging in for the underbust. For the bust, it should be level and just touching, not compressing the breast tissue.

7. Can I measure myself over clothes?

For the most accurate results, measure without a bra or with a thin, non-padded bra.

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

Measure based on the larger breast for cup size, and consider bras with stretch lace or removable padding to adjust the fit for the smaller side.

Related Tools and Internal Resources

• Comprehensive Bra Fitting Guide: Learn the signs of a good and bad bra fit.
• Bra Style Guide: Discover different bra styles and which might suit your shape and needs.
• International Bra Size Conversion Chart: Convert between US, UK, EU, and other sizing systems.
• How to Measure Bra Size Video Tutorial: A visual guide to taking accurate measurements.
• Bra Care Tips: Extend the life of your bras with proper care.
• Understanding Breast Shape: Learn how breast shape affects bra fit.