Find your perfect fit with our easy-to-use calculator.
Inches
Inches
Fullest part of bust
Upper part of bust
Understanding Bra Sizing
Finding the right bra size is crucial for comfort, support, and overall breast health. A bra that fits correctly can prevent back pain, shoulder strain, and discomfort. The most common bra sizing system involves two components: the band size and the cup size.
Band Size Calculation:
The band size is determined by your underbust measurement. It's the number part of your bra size (e.g., 34, 36, 38). A properly fitted band should be snug and sit parallel to the ground, providing the primary support for the bra.
Our calculator takes your Underbust Measurement directly. This measurement should be taken snugly around your torso, directly beneath your breasts. If you are between sizes, it's often recommended to go up to the next even number, as bra bands can stretch over time. However, modern calculators often use a direct measurement or a slight adjustment based on how snug the tape measure feels.
For a more precise fit, we also ask for your Ribcage Measurement (across chest). This helps to ensure the band is not too tight or too loose, as individual torso shapes vary. A good band will typically sit parallel to the floor and allow you to fit no more than two fingers underneath it.
Cup Size Calculation:
The cup size is determined by the difference between your bust measurement (taken at the fullest part of your breast) and your band size (or underbust measurement). It's the letter part of your bra size (e.g., A, B, C, D).
The formula for calculating the cup size is generally:
Cup Size = Bust Measurement - Band Size (Underbust Measurement)
The resulting difference in inches typically corresponds to a cup letter:
1 inch difference = A cup
2 inches difference = B cup
3 inches difference = C cup
4 inches difference = D cup
5 inches difference = DD cup
And so on, with each additional inch usually representing a subsequent cup size (e.g., DDD, G, H, etc., though sizing can vary by brand).
Our calculator uses the Ribcage Measurement (across chest) to determine the bust measurement and then calculates the difference from the underbust measurement to derive the cup size. We ask for the Cup Measurement Point to ensure you are measuring accurately at the fullest part of your bust.
Important Considerations:
Variations by Brand: Bra sizing can differ significantly between brands and even styles within the same brand. Always try bras on when possible.
Body Shape: Factors like breast shape (e.g., teardrop, round, East-West) and torso structure can influence how a bra fits.
Measurement Method: Ensure you are using a flexible, non-stretch measuring tape and keeping it level. Don't pull the tape too tight or too loose.
Comfort is Key: The most important factor is how the bra feels. If it's digging in, gaping, or riding up, it's likely not the right fit, regardless of the calculated size.
This calculator provides a starting point. For the most accurate results, consult with a professional fitter.
function calculateBraSize() {
var underbust = parseFloat(document.getElementById("bandUnderbust").value);
var ribcage = parseFloat(document.getElementById("bandRibcage").value);
var cupPoint = document.getElementById("cupMeasurePoint").value;
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
resultDiv.classList.remove("error");
var bandResult = "";
var cupResult = "";
var braSize = "";
// — Band Size Calculation —
// This is a simplified model. Real band sizing involves a lookup table and adjustments.
// A common approach is to round down to the nearest even number.
if (!isNaN(underbust) && underbust > 0) {
if (underbust % 2 !== 0) {
bandResult = Math.floor(underbust); // Round down if odd
} else {
bandResult = underbust;
}
// Additional check to ensure the band isn't too tight relative to ribcage measurement
if (!isNaN(ribcage) && ribcage > 0 && bandResult 0 && bandResult > ribcage – 4) {
resultDiv.innerHTML = "Band size seems too large for your ribcage measurement. Please re-measure.";
resultDiv.classList.add("error");
return;
}
} else {
resultDiv.innerHTML = "Please enter a valid underbust measurement.";
resultDiv.classList.add("error");
return;
}
// — Cup Size Calculation —
if (!isNaN(ribcage) && ribcage > 0 && !isNaN(bandResult) && bandResult > 0) {
var difference = ribcage – bandResult;
var cupSizeValue = Math.round(difference); // Round to nearest inch for common sizing
switch (cupSizeValue) {
case 0: cupResult = "AA"; break; // Less common, but possible
case 1: cupResult = "A"; break;
case 2: cupResult = "B"; break;
case 3: cupResult = "C"; break;
case 4: cupResult = "D"; break;
case 5: cupResult = "DD"; break; // Or E depending on region
case 6: cupResult = "DDD"; break; // Or F
case 7: cupResult = "G"; break;
case 8: cupResult = "H"; break;
case 9: cupResult = "I"; break;
case 10: cupResult = "J"; break;
default:
if (cupSizeValue > 10) {
cupResult = "K+ (Please consult a professional)";
} else if (cupSizeValue < 0) {
cupResult = "Invalid measurement difference";
}
break;
}
} else {
resultDiv.innerHTML = "Please enter valid measurements for both underbust and ribcage.";
resultDiv.classList.add("error");
return;
}
// — Final Bra Size —
if (bandResult && cupResult && !cupResult.includes("Invalid") && !cupResult.includes("Please")) {
braSize = bandResult + "" + cupResult;
resultDiv.innerHTML = "Your estimated bra size is: " + braSize + "";
} else if (cupResult.includes("Please")) {
resultDiv.innerHTML = "Your estimated band size is: " + bandResult + ". Cup size requires professional fitting.";
}
else {
resultDiv.innerHTML = "Could not calculate bra size. Please check your measurements.";
resultDiv.classList.add("error");
}
}