Finding the right bra size is crucial for comfort, support, and overall well-being. The American bra sizing system primarily uses two measurements: the band size and the cup size. This calculator helps you determine your estimated bra size based on these measurements.
How It Works: The Math Behind the Size
The calculation involves two main steps:
Band Size: This is determined by measuring snugly around your rib cage, directly under your bust. The measurement is typically rounded to the nearest even number (e.g., 30, 32, 34 inches). The calculator takes your input and directly uses it, assuming it's already calibrated to the standard band sizing.
Cup Size: This is determined by finding the difference between your bust measurement (taken at the fullest part of your chest) and your band measurement. The difference in inches corresponds to a letter size:
0-1 inches: AA Cup
1 inch: A Cup
2 inches: B Cup
3 inches: C Cup
4 inches: D Cup
5 inches: DD Cup (or E Cup in some systems)
6 inches: DDD Cup (or F Cup)
And so on, typically increasing by 1 inch for each subsequent letter (E, F, G, etc., though these can vary by brand).
The formula for the cup size letter is essentially: Cup Size = Bust Measurement – Band Measurement.
Your final bra size is a combination of your band size and your calculated cup size (e.g., 34C).
Important Considerations:
Accuracy of Measurements: Ensure you are wearing a non-padded bra when taking measurements, and that the measuring tape is level and snug but not digging into your skin.
Variations in Brands: Bra sizing can vary significantly between different brands and even different styles within the same brand. This calculator provides an excellent starting point, but fitting is always key.
Body Shape: Different body shapes might require adjustments. For instance, if you have a very wide-set bust or very close-set bust, you might need to try sizes slightly different from the calculated one.
Consult a Professional: For the most accurate fit, consider visiting a professional lingerie store for a bra fitting.
Use this calculator as a guide to understand your potential bra size and to make more informed choices when shopping for lingerie.
function calculateBraSize() {
var bandMeasurementInput = document.getElementById("bandMeasurement");
var bustMeasurementInput = document.getElementById("bustMeasurement");
var resultDiv = document.getElementById("result");
// Clear previous results and error messages
resultDiv.innerHTML = "";
var bandMeasurement = parseFloat(bandMeasurementInput.value);
var bustMeasurement = parseFloat(bustMeasurementInput.value);
// Input validation
if (isNaN(bandMeasurement) || bandMeasurement <= 0) {
resultDiv.innerHTML = "Please enter a valid band measurement.";
return;
}
if (isNaN(bustMeasurement) || bustMeasurement <= 0) {
resultDiv.innerHTML = "Please enter a valid bust measurement.";
return;
}
if (bustMeasurement <= bandMeasurement) {
resultDiv.innerHTML = "Bust measurement must be larger than band measurement.";
return;
}
// Determine Band Size (rounded to nearest even number)
var bandSize = Math.round(bandMeasurement);
if (bandSize % 2 !== 0) {
// If the rounded value is odd, we need to decide whether to round up or down.
// A common practice is to round to the nearest even number.
// If bandMeasurement is exactly between two even numbers (e.g., 31.5),
// it would round to 32. If it's 30.5, it rounds to 30.
// We will ensure it's even by adjusting.
if (bandSize + 1 <= bandMeasurement + 1) { // Check if rounding up is closer or equally close
bandSize += 1;
} else {
bandSize -= 1;
}
}
// Ensure band size is not less than a reasonable minimum like 28
if (bandSize < 28) {
bandSize = 28;
}
// Calculate Cup Size Difference
var cupDifference = bustMeasurement – bandMeasurement;
var cupSize = "";
if (cupDifference = 1 && cupDifference = 2 && cupDifference = 3 && cupDifference = 4 && cupDifference = 5 && cupDifference = 6 && cupDifference = 7 && cupDifference = 8 && cupDifference = 9 && cupDifference = 10 && cupDifference < 11) {
cupSize = "J";
} else {
// For very large differences, indicate it might be beyond standard sizing or use a general large cup
cupSize = "K+ (or larger)";
}
var braSize = bandSize + cupSize;
resultDiv.innerHTML = braSize + "Based on your measurements";
}