What is My Bra Size Calculator
Find Your Perfect Fit Instantly
Bra Size Calculator
Measure snugly around your ribcage, directly under your bust. Keep the tape measure level.
Measure loosely around the fullest part of your bust, keeping the tape measure parallel to the ground.
Standard (Full Coverage)
Balconette
Push-Up
Minimizer
Different styles can affect fit. Standard is recommended for initial calculation.
Your Estimated Bra Size
Estimated Bra Size
Band: |
Cup: |
Difference: inches
Formula: Band Size is your underbust measurement (rounded to nearest even number). Cup Size is determined by the difference between your bust and band measurements.
Bra Size Fit Guide
| Measurement | Value | Unit |
|---|---|---|
| Underbust Measurement | inches | |
| Overbust Measurement | inches | |
| Difference (Bust – Band) | inches | |
| Calculated Band Size | inches | |
| Calculated Cup Size |
What is My Bra Size Calculator?
The "What is My Bra Size Calculator" is a digital tool designed to help individuals determine their most likely bra size based on simple body measurements. It simplifies the often confusing process of bra fitting by applying a standardized formula. This calculator is particularly useful for those who are unsure of their current size, experiencing fit issues with existing bras, or shopping for bras online where trying them on isn't possible. It provides a starting point for finding a comfortable and supportive bra, which is crucial for both comfort and breast health.
Many people wear the wrong bra size, leading to discomfort, poor support, and even physical pain. This can be due to a lack of understanding of how bras should fit, changes in body shape, or simply not knowing the correct measurement techniques. A bra size calculator aims to demystify this process, offering a quick and accessible way to get an estimated size. It's important to remember that this is an estimation, and individual bra styles and brands can vary, but it serves as an excellent foundation for your bra fitting journey.
Who Should Use It?
Anyone who:
- Is new to wearing bras.
- Has never been professionally fitted.
- Is experiencing discomfort or poor fit with their current bras (e.g., straps digging in, band riding up, cups gapping or overflowing).
- Has undergone significant body changes (weight fluctuations, pregnancy, hormonal changes).
- Is shopping for bras online and wants a reliable starting size.
- Wants to understand the basic principles of bra sizing.
Common Misconceptions
- "My size never changes.": Body shape and size can fluctuate due to weight, hormones, and age.
- "All bras of the same size fit the same.": Different brands, styles (balconette, push-up, full coverage), and materials can significantly alter the fit.
- "A tight band is bad.": The band provides the primary support (about 80%). It should be snug but comfortable, allowing only a finger or two underneath.
- "The calculator is 100% accurate.": It's an estimation tool. A professional fitting is always recommended for the most precise fit.
Bra Size Formula and Mathematical Explanation
The standard bra size calculation involves two main components: the band size and the cup size. While variations exist, the most common method relies on simple arithmetic using measurements taken in inches.
Step-by-Step Derivation
- Measure the Band Size: Wrap a flexible measuring tape snugly around your ribcage directly under your bust. Ensure the tape is level all the way around. This measurement is your underbust measurement.
- Round the Band Measurement: If your underbust measurement is not an even number, round it to the nearest even number (e.g., 31 inches rounds up to 32, 32.5 inches rounds down to 32). This rounded number is your calculated band size.
- Measure the Bust Size: Wrap the measuring tape loosely around the fullest part of your bust (nipple area). Keep the tape measure parallel to the ground.
- Calculate the Difference: Subtract your underbust measurement (from step 1, before rounding) from your overbust measurement (from step 3).
- Determine the Cup Size: The difference calculated in step 4 corresponds to a cup size. The standard US sizing is as follows:
- 0-1 inch difference = AA cup
- 1 inch difference = A cup
- 2 inch difference = B cup
- 3 inch difference = C cup
- 4 inch difference = D cup
- 5 inch difference = DD (or E) cup
- And so on, typically adding a cup size for each additional inch.
- Combine Band and Cup: Your bra size is the combination of your calculated band size (from step 2) and your determined cup size (from step 5). For example, a 32-inch band and a 35-inch bust (3-inch difference) would result in a 32C bra size.
Variable Explanations
The core variables used in the bra size calculation are straightforward measurements:
- Underbust Measurement: The circumference of your ribcage directly below the breasts.
- Overbust Measurement: The circumference of your body over the fullest part of your breasts.
- Difference: The numerical difference between the overbust and underbust measurements.
- Band Size: The determined band size, usually rounded from the underbust measurement.
- Cup Size: The letter designation determined by the difference between bust and band measurements.
Variables Table
| Variable | Meaning | Unit | Typical Range |
|---|---|---|---|
| Underbust Measurement | Circumference around the ribcage below the breasts. | Inches | 26 – 50+ |
| Overbust Measurement | Circumference around the fullest part of the bust. | Inches | 28 – 60+ |
| Difference | Overbust Measurement – Underbust Measurement. | Inches | 0 – 15+ |
| Band Size | Calculated band size, typically rounded to the nearest even number. | Inches | 28 – 50+ |
| Cup Size | Letter designation based on the difference. | Letter (e.g., A, B, C, D) | AA, A, B, C, D, DD, E, F, G… |
Practical Examples (Real-World Use Cases)
Example 1: Standard Fit
Scenario: Sarah is experiencing discomfort with her current bras. The straps keep slipping, and the band feels too loose.
Inputs:
- Underbust Measurement: 34 inches
- Overbust Measurement: 37 inches
- Bra Style: Standard
Calculation:
- Band Measurement: 34 inches (already an even number, so Band Size = 34)
- Bust Measurement: 37 inches
- Difference: 37 – 34 = 3 inches
- Cup Size: A 3-inch difference corresponds to a C cup.
Calculator Output:
- Estimated Bra Size: 34C
- Intermediate Values: Band: 34, Cup: C, Difference: 3 inches
Interpretation: Sarah's current bra size might be incorrect. The calculator suggests she should try a 34C. This size offers a band that fits snugly around her ribcage and a cup size that accommodates the difference between her bust and band measurements, potentially resolving her fit issues.
Example 2: Larger Difference
Scenario: Maria is looking to buy a new bra online and wants to confirm her size.
Inputs:
- Underbust Measurement: 38 inches
- Overbust Measurement: 45 inches
- Bra Style: Standard
Calculation:
- Band Measurement: 38 inches (already an even number, so Band Size = 38)
- Bust Measurement: 45 inches
- Difference: 45 – 38 = 7 inches
- Cup Size: A 7-inch difference typically corresponds to an F cup (following the pattern: D=4, DD=5, E=6, F=7).
Calculator Output:
- Estimated Bra Size: 38F
- Intermediate Values: Band: 38, Cup: F, Difference: 7 inches
Interpretation: The calculator indicates Maria's likely bra size is 38F. This size is designed for individuals with a larger frame and a significant difference between their underbust and overbust measurements, suggesting she should look for bras in this range. It's important for Maria to note that F cups can vary greatly by brand, so trying on is still recommended.
How to Use This Bra Size Calculator
Using the bra size calculator is simple and takes just a few minutes. Follow these steps for an accurate estimation:
- Gather Your Tools: You'll need a flexible measuring tape (like one used for sewing) and a mirror. Ensure you are not wearing a padded or push-up bra; a non-padded, comfortable bra or no bra at all is best for accurate measurements.
- Measure Your Band: Place the measuring tape snugly around your ribcage directly under your bust. The tape should be level and snug but not digging into your skin. Note this measurement in inches.
- Measure Your Bust: Wrap the tape measure loosely around the fullest part of your bust, usually over the nipples. Ensure the tape remains parallel to the ground and isn't too tight. Note this measurement in inches.
- Enter Measurements: Input your underbust measurement into the "Band Measurement (Underbust)" field and your overbust measurement into the "Bust Measurement (Overbust)" field on the calculator.
- Select Bra Style (Optional but Recommended): Choose the bra style you typically wear or are interested in. "Standard" is a good default for general sizing.
- Calculate: Click the "Calculate Size" button.
How to Read Results
The calculator will display your estimated bra size prominently. This includes:
- Primary Result: Your estimated bra size (e.g., 34C).
- Intermediate Values:
- Band: Your calculated band size (e.g., 34 inches).
- Cup: Your calculated cup size (e.g., C).
- Difference: The numerical difference between your bust and band measurements (e.g., 3 inches).
- Table Breakdown: A table provides a clear summary of all measurements and calculations.
- Chart: A visual guide helps understand how the difference relates to cup size.
Decision-Making Guidance
Use the estimated size as a starting point. If the calculator suggests a size significantly different from what you currently wear, it's a strong indicator you may need to adjust. Consider the following:
- Band Fit: The band should feel snug and supportive, sitting parallel to the ground. If it rides up, the band might be too large.
- Cup Fit: The cups should fully contain your breasts without gaping or spilling over. If there's overflow, the cup size might be too small. If there's gapping, it might be too large.
- Straps: Straps should stay in place without digging into your shoulders.
- Brand Variations: Remember that sizing can differ between brands. If possible, try on bras from different brands in your estimated size.
- Professional Fitting: For the most accurate fit, consider visiting a lingerie store for a professional fitting.
Key Factors That Affect Bra Size Results
While the calculator provides a solid estimate, several factors can influence your actual bra size and fit. Understanding these can help you fine-tune your search for the perfect bra.
- Body Composition and Tissue Density: The calculator relies purely on circumference measurements. However, breast tissue density (how firm or soft it is) and how it's distributed can affect how a bra fits. Softer tissue might require more supportive styles, while denser tissue might fit differently in the same cup size.
- Bra Style and Design: Different bra styles are designed for different shapes and support needs. A full-coverage bra will fit differently than a balconette or a plunge style, even in the same calculated size. The calculator provides a baseline, but style choice is crucial for optimal fit.
- Brand Sizing Variations: This is a significant factor. European, UK, and US sizing systems differ, and even within a single country, brands can have unique sizing charts and fits. A 34C in one brand might fit like a 32D or 36B in another.
- Changes in Body Weight: Fluctuations in weight can affect both the underbust and overbust measurements. Weight gain might increase both measurements, potentially requiring a larger band and cup size. Weight loss might decrease both, necessitating a smaller size.
- Hormonal Changes and Life Stages: Hormonal fluctuations, such as those during the menstrual cycle, pregnancy, breastfeeding, or menopause, can cause temporary or permanent changes in breast size and shape. This means your bra size might need adjustment periodically.
- Posture and Body Shape: While not directly measured by the calculator, posture (e.g., slouching vs. standing tall) can slightly alter measurements. Additionally, torso length and shape can influence how a bra band sits and feels.
- Wear and Tear: Over time, bra bands can stretch out, and cups can lose their shape. A bra that once fit perfectly might no longer do so due to age and frequent use.
Frequently Asked Questions (FAQ)
Q1: How often should I measure my bra size?
A: It's recommended to measure your bra size at least once a year, or whenever you notice changes in your body weight, experience hormonal shifts, or find your current bras don't fit comfortably anymore.
Q2: Can I use this calculator if I'm pregnant or breastfeeding?
A: While the calculator can provide a starting point, breast size often changes significantly during pregnancy and breastfeeding. It's best to get measured professionally during these times, as your size may fluctuate daily.
Q3: My calculated size feels wrong. What should I do?
A: The calculator provides an estimate. Try the suggested size, but pay close attention to the fit. If it's still uncomfortable, consider trying sister sizes (e.g., if 34C feels too tight in the band, try 36B; if the cup feels too small, try 34D). A professional fitting is the best way to resolve persistent fit issues.
Q4: What are "sister sizes"?
A: Sister sizes are bra sizes that have the same cup volume but different band sizes. For example, 32D, 34C, and 36B are sister sizes. If a bra band is too tight, you go up a band size and down a cup size (32D to 34C). If the band is too loose, you go down a band size and up a cup size (34C to 32D).
Q5: Does the calculator account for different countries' sizing systems?
A: This calculator primarily uses the standard US sizing convention (inches for measurements, standard letter progression for cups). Sizing can vary significantly in the UK, EU, and other regions. Always check the specific brand's sizing chart.
Q6: What does it mean if my breasts spill out of the cups?
A: If your breasts are spilling out of the top or sides of the cups, it generally means the cup size is too small for your current band size. You may need to go up one or two cup sizes while keeping the band size the same (e.g., moving from a 34C to a 34D or 34DD).
Q7: What if there's a gap in the top of the cup?
A: Gapping in the cup often indicates that the cup size is too large for your band size, or the bra style isn't suitable for your breast shape. Try going down a cup size with the same band size (e.g., from a 34D to a 34C).
Q8: How important is the band for bra support?
A: The band is crucial for support, providing approximately 80% of it. A well-fitting band should be snug enough to stay in place without riding up, allowing you to fit only one or two fingers underneath comfortably. If the band feels loose, the bra is likely not providing adequate support, regardless of the cup size.
Related Tools and Internal Resources
- Bra Size Calculator Instantly estimate your bra size based on your measurements.
- Guide to Bra Styles Learn the differences between balconette, push-up, full coverage, and more.
- How to Care for Your Bras Extend the life of your lingerie with proper washing and storage techniques.
- Choosing the Best Sports Bra Essential tips for selecting the right support for your workout intensity.
- Avoid Common Bra Fitting Mistakes Learn what to look for and what to avoid when trying on bras.
- Lingerie Fabrics Explained A deep dive into materials like lace, cotton, microfiber, and their benefits.
';
legendHtml += ' Difference'; // Placeholder for icon
legendHtml += ' Band Size'; // Placeholder for icon
legendHtml += '
';
document.getElementById('chartLegend').innerHTML = legendHtml;
}
function getCupSize(difference) {
if (difference <= 0.5) return 'AA';
if (difference <= 1.5) return 'A';
if (difference <= 2.5) return 'B';
if (difference <= 3.5) return 'C';
if (difference <= 4.5) return 'D';
if (difference <= 5.5) return 'DD'; // UK E
if (difference <= 6.5) return 'E'; // UK F
if (difference <= 7.5) return 'F'; // UK G
if (difference <= 8.5) return 'G'; // UK H
if (difference <= 9.5) return 'H'; // UK I
if (difference <= 10.5) return 'I'; // UK J
if (difference <= 11.5) return 'J'; // UK K
if (difference <= 12.5) return 'K'; // UK L
return 'Custom'; // For very large differences
}
function validateInput(value, id, min, max, errorMessageId, fieldName) {
var errorElement = document.getElementById(errorMessageId);
errorElement.classList.remove('visible');
errorElement.textContent = '';
if (value === '') {
errorElement.textContent = fieldName + ' cannot be empty.';
errorElement.classList.add('visible');
return false;
}
var numValue = parseFloat(value);
if (isNaN(numValue)) {
errorElement.textContent = fieldName + ' must be a number.';
errorElement.classList.add('visible');
return false;
}
if (numValue max) {
errorElement.textContent = fieldName + ' must be between ' + min + ' and ' + max + ' inches.';
errorElement.classList.add('visible');
return false;
}
return true;
}
function calculateBraSize() {
var bandMeasurement = bandMeasurementInput.value;
var bustMeasurement = bustMeasurementInput.value;
var braStyle = braStyleSelect.value;
var bandError = document.getElementById('bandMeasurementError');
var bustError = document.getElementById('bustMeasurementError');
bandError.classList.remove('visible');
bustError.classList.remove('visible');
var isValidBand = validateInput(bandMeasurement, 'bandMeasurement', 26, 50, 'bandMeasurementError', 'Band Measurement');
var isValidBust = validateInput(bustMeasurement, 'bustMeasurement', 28, 60, 'bustMeasurementError', 'Bust Measurement');
if (!isValidBand || !isValidBust) {
resultDiv.style.display = 'none';
return;
}
var numBand = parseFloat(bandMeasurement);
var numBust = parseFloat(bustMeasurement);
var calculatedBandSize = Math.round(numBand / 2) * 2; // Round to nearest even number
var difference = numBust – numBand;
var cupSize = getCupSize(difference);
primaryResultDiv.textContent = calculatedBandSize + cupSize;
bandResultSpan.textContent = calculatedBandSize;
cupResultSpan.textContent = cupSize;
differenceResultSpan.textContent = difference.toFixed(1);
tableBandValue.textContent = numBand.toFixed(1);
tableBustValue.textContent = numBust.toFixed(1);
tableDifferenceValue.textContent = difference.toFixed(1);
tableCalculatedBand.textContent = calculatedBandSize;
tableCalculatedCup.textContent = cupSize;
resultDiv.style.display = 'block';
// Update chart data
var cupIndex = chartData.labels.indexOf(cupSize);
if (cupIndex === -1) { // If custom cup size, find nearest standard
if (cupSize === 'AA') cupIndex = 0;
else if (cupSize === 'A') cupIndex = 1;
else if (cupSize === 'B') cupIndex = 2;
else if (cupSize === 'C') cupIndex = 3;
else if (cupSize === 'D') cupIndex = 4;
else if (cupSize === 'DD') cupIndex = 5;
else if (cupSize === 'E') cupIndex = 6;
else if (cupSize === 'F') cupIndex = 7;
else if (cupSize === 'G') cupIndex = 8;
else cupIndex = 4; // Default to D if not found
}
// Adjust dataset values for visualization
var updatedDifferenceData = chartData.labels.map(function(label, index) {
var diff = getCupSizeDifference(label);
return diff;
});
chart.data.datasets[0].data = updatedDifferenceData;
// Highlight the calculated band size on the chart (conceptually)
// For simplicity, we'll just update the label text for the band size dataset
chart.data.datasets[1].data = chartData.labels.map(function() { return calculatedBandSize; });
chart.data.datasets[1].label = 'Band Size: ' + calculatedBandSize;
chart.update();
updateChartLegend(); // Ensure legend reflects dynamic band size label
}
function getCupSizeDifference(cupLabel) {
switch(cupLabel) {
case 'AA': return 0.5;
case 'A': return 1;
case 'B': return 2;
case 'C': return 3;
case 'D': return 4;
case 'DD': return 5;
case 'E': return 5.5; // Approximation for UK E
case 'F': return 6.5; // Approximation for UK F
case 'G': return 7.5; // Approximation for UK G
default: return 0;
}
}
function resetCalculator() {
bandMeasurementInput.value = '34';
bustMeasurementInput.value = '37';
braStyleSelect.value = 'standard';
resultDiv.style.display = 'none';
document.getElementById('bandMeasurementError').classList.remove('visible');
document.getElementById('bustMeasurementError').classList.remove('visible');
calculateBraSize(); // Recalculate with defaults
}
function copyResults() {
var bandMeasurement = bandMeasurementInput.value;
var bustMeasurement = bustMeasurementInput.value;
var braStyle = braStyleSelect.value;
var numBand = parseFloat(bandMeasurement);
var numBust = parseFloat(bustMeasurement);
var calculatedBandSize = Math.round(numBand / 2) * 2;
var difference = numBust – numBand;
var cupSize = getCupSize(difference);
var resultText = "— Bra Size Calculation —\n\n";
resultText += "Inputs:\n";
resultText += "- Underbust Measurement: " + bandMeasurement + " inches\n";
resultText += "- Overbust Measurement: " + bustMeasurement + " inches\n";
resultText += "- Bra Style: " + braStyle + "\n\n";
resultText += "Results:\n";
resultText += "Estimated Bra Size: " + calculatedBandSize + cupSize + "\n";
resultText += "Band Size: " + calculatedBandSize + " inches\n";
resultText += "Cup Size: " + cupSize + "\n";
resultText += "Measurement Difference: " + difference.toFixed(1) + " inches\n\n";
resultText += "Formula Used: Band size is underbust measurement rounded to the nearest even number. Cup size is determined by the difference between bust and band measurements.";
navigator.clipboard.writeText(resultText).then(function() {
alert('Results copied to clipboard!');
}).catch(function(err) {
console.error('Failed to copy results: ', err);
alert('Failed to copy results. Please copy manually.');
});
}
function toggleFaq(element) {
var parent = element.parentElement;
parent.classList.toggle('open');
}
// Initialize chart on load
window.onload = function() {
initializeChart();
resetCalculator(); // Set initial values and calculate
};
// Add event listeners for real-time updates
bandMeasurementInput.addEventListener('input', calculateBraSize);
bustMeasurementInput.addEventListener('input', calculateBraSize);
braStyleSelect.addEventListener('change', calculateBraSize);