📏 Bra Size Calculator 2026 - Find Your Perfect Fit Instantly
📊 Understanding Bra Size Calculations
A bra size calculator is your essential digital tool for determining the exact bra size that will fit you perfectly. In 2026, finding the right bra size shouldn't require guesswork or uncomfortable fitting room experiences. This calculator uses your underbust (band) and bust measurements to mathematically determine your ideal size using both UK and US sizing methods.
Whether you're shopping online, experiencing body changes, or simply tired of ill-fitting bras, this tool delivers accurate results in seconds. With approximately 80% of people wearing the wrong bra size, our calculator eliminates confusion and helps you find bras that provide proper support, comfort, and confidence.
🧮 Bra Size Calculator Tool
📝 How to Use the Bra Size Calculator
- Select Your Sizing Method: Choose between UK Method (uses actual underbust measurement) or US Method (adds inches to underbust). The UK method is generally more accurate for modern stretchy bras.
- Choose Your Measurement Unit: Select either inches or centimeters from the dropdown menu based on your measuring tape.
- Enter Your Underbust Measurement: Measure directly under your bust, where your bra band sits. Keep the tape snug but comfortable.
- Enter Your Bust Measurement: Measure around the fullest part of your bust, typically across the nipples. Keep tape parallel to the floor.
- Click Calculate: The calculator will instantly display your band size, cup size, and sister sizes for alternative fitting options.
- Review Your Results: Note both your calculated size and sister sizes for flexibility when shopping different brands.
⚠️ Common Mistake to Avoid: Never measure while wearing a padded or push-up bra - this adds bulk and produces inaccurate bust measurements. Measure with a non-padded bra or no bra for best results.
📐 Bra Size Formula & Calculation Method
UK Method - Band Size Calculation
The UK method uses your raw underbust measurement, rounding to the nearest even number. Example: 33" underbust becomes 34 band. This provides a snugger, more supportive fit.
Cup Size Calculation
Each inch of difference equals one cup size: 1"=A, 2"=B, 3"=C, 4"=D, 5"=DD, 6"=E, 7"=F, 8"=FF, etc.
US Method - Band Size Calculation
The US method adds 4-5 inches to your underbust. This historically accounted for less stretchy materials but may produce larger band sizes with modern bras.
Sister Size Formula
Sister sizes maintain the same cup volume while changing the band. Example: 34C, 32D, and 36B are all sister sizes.
📊 Bra Size Calculation Examples
Example 1: Sarah - Average Build (UK Method)
Measurements: Underbust = 32", Bust = 36"
Step 2: Cup Difference = 36 − 32 = 4"
Step 3: 4 inches = D cup
Example 2: Maria - Fuller Figure (UK Method)
Measurements: Underbust = 38", Bust = 46"
Step 2: Cup Difference = 46 − 38 = 8"
Step 3: 8 inches = FF cup
Example 3: Emma - Petite Frame (US Method)
Measurements: Underbust = 27", Bust = 32"
Step 2: Cup Difference = 32 − 32 = 0"
Step 3: 0 inches = AA cup
Note: UK method would give 28D - quite different!
📊 International Bra Size Conversion Chart 2026
Band Size Conversions
| UK/US Band | EU Band | FR Band | AU/NZ Band | JP Band |
|---|---|---|---|---|
| 28 | 60 | 75 | 6 | 60 |
| 30 | 65 | 80 | 8 | 65 |
| 32 | 70 | 85 | 10 | 70 |
| 34 | 75 | 90 | 12 | 75 |
| 36 | 80 | 95 | 14 | 80 |
| 38 | 85 | 100 | 16 | 85 |
| 40 | 90 | 105 | 18 | 90 |
| 42 | 95 | 110 | 20 | 95 |
Cup Size Conversions
| Difference | UK Cup | US Cup | EU Cup |
|---|---|---|---|
| 0" | AA | AA | AA |
| 1" | A | A | A |
| 2" | B | B | B |
| 3" | C | C | C |
| 4" | D | D | D |
| 5" | DD | DD/E | E |
| 6" | E | DDD/F | F |
| 7" | F | G | G |
| 8" | FF | H | H |
| 9" | G | I | I |
Source: International sizing standards based on ISO/TR 10652:1991
💡 Important Tips for Accurate Bra Sizing
- Measure at the right time: Avoid measuring during your period when breasts may be swollen. Mid-cycle measurements are most consistent.
- Re-measure regularly: Your bra size can change with weight fluctuations, hormones, pregnancy, and aging. Check every 6-12 months.
- Band fit is crucial: The band provides 80% of support. It should be snug on the loosest hook when new.
- Try sister sizes: If your exact size isn't available or doesn't feel right, sister sizes offer the same cup volume.
- Brand variation exists: Sizes vary between manufacturers. You may need different sizes for different brands.
- Consider bra style: Plunge, balconette, sports, and full-cup bras fit differently. You may need different sizes for different styles.
❓ Frequently Asked Questions
The main difference lies in band size calculation. UK sizing uses your actual underbust rounded to the nearest even number, while US sizing adds 4-5 inches. Example: 32" underbust = 32 band (UK) but ~36 band (US). The UK method is generally more accurate for modern elastic bras.
Recalculate every 6-12 months as routine. Also remeasure after weight changes of 10+ pounds, pregnancy, breastfeeding, hormonal changes, or menopause. If your current bras feel uncomfortable or ride up, it's time to remeasure.
Sister sizes have the same cup volume but different band sizes. When you go down one band, go up one cup (and vice versa). Example: 34C, 32D, and 36B are sister sizes. Use them when your exact size is unavailable or when trying different brands.
Online calculators are highly accurate when you provide correct measurements. The formulas are the same as professional fitters use. Accuracy depends on how well you measure yourself. Measure without padding, keep tape level, and don't compress breast tissue.
Bra sizing isn't standardized across brands. Different manufacturers use different methodologies, fabric stretch levels, cup shapes, and quality control. A 34C at one brand may fit differently than at another. Always check brand-specific charts.
Measure with either no bra or a thin, non-padded bra. Padded, push-up, or heavily molded cups add bulk that throws off your bust measurement. For underbust, it doesn't matter, but choose the thinnest option for bust measurement.
A riding-up band indicates your band size is too large. The band provides 80% of support and should sit level. Try going down one or two band sizes while going up in cup size (sister sizing). The band should be snug on the loosest hook when new.
Yes, it's normal for breast size to fluctuate during your cycle due to hormones. Many experience temporary swelling before their period, making bras feel tighter. Having bras in sister sizes can help. Measure mid-cycle for baseline sizing.
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Created by OmniCalculator.space | Last Updated: February 2026