Determining the correct bra cup size is essential for comfort, support, and a flattering silhouette. While bra sizing can vary significantly between brands and styles, the fundamental calculation is based on the difference between your bust and band measurements. This calculator uses the standard US bra sizing method.
How the Calculation Works (US Standard):
The process involves two key measurements:
Band Measurement: This is the measurement around your ribcage, directly under your bust. It forms the 'number' part of your bra size (e.g., 34, 36, 38). The band should be snug but comfortable, parallel to the floor, and should not dig in.
Bust Measurement: This is the measurement around the fullest part of your bust, usually over the nipples, with a soft measuring tape. Ensure the tape is level all around and not too tight.
The cup size is determined by the difference between your bust measurement and your band measurement. Each inch of difference typically corresponds to a letter cup size.
US Cup Size Chart (Based on Difference):
0 inches difference: AA Cup
1 inch difference: A Cup
2 inches difference: B Cup
3 inches difference: C Cup
4 inches difference: D Cup
5 inches difference: DD (or E) Cup
6 inches difference: DDD (or F) Cup
7 inches difference: G Cup
And so on… (Each additional inch generally adds a letter, though sizing can become less standardized at larger cup sizes).
The Calculation Formula:
Cup Size Letter = RoundDown((Bust Measurement - Band Measurement) / 1 inch)
Then, map the resulting number to the cup size letter using the chart above.
Important Considerations:
Brand Variations: Sizes can differ wildly between brands. What's a C in one brand might be a D in another.
Bra Style: Different bra styles (balconette, plunge, full coverage) fit differently and can affect perceived size.
Fit is Key: This calculator provides an estimate. The best way to find your perfect fit is to try on bras and assess how they feel and look. A well-fitting bra should feel secure, comfortable, and lift the bust without spilling out or creating gaps.
Professional Fitting: If unsure, consider getting professionally measured at a reputable lingerie store.
Use this calculator as a starting point to better understand your measurements and to help guide your bra shopping. Happy shopping!
function calculateCupSize() {
var bandMeasurement = parseFloat(document.getElementById("bandMeasurement").value);
var bustMeasurement = parseFloat(document.getElementById("bustMeasurement").value);
var resultDiv = document.getElementById("result");
// Clear previous results
resultDiv.innerHTML = "";
// Input validation
if (isNaN(bandMeasurement) || isNaN(bustMeasurement)) {
resultDiv.innerHTML = "Please enter valid numbers for both measurements.";
return;
}
if (bandMeasurement <= 0 || bustMeasurement <= 0) {
resultDiv.innerHTML = "Measurements must be positive values.";
return;
}
if (bustMeasurement 13) {
// For very large differences, indicate it's beyond standard chart or complex
cupSizeLetter = `Larger (approx. ${cupSizeNumber}+)`;
} else {
// Fallback for unexpected values, though should be covered by above
cupSizeLetter = "Unknown";
}
// Display the result
resultDiv.innerHTML = "Your estimated US Cup Size: " + bandMeasurement + cupSizeLetter + "";
}