Find your perfect fit with professional measurements
Measure tightly around your ribcage, just below your breasts.
Measure around the fullest part of your chest while wearing a non-padded bra.
Your Estimated Bra Size Is:
How to Measure for a Bra Properly
Wearing the wrong bra size isn't just uncomfortable—it can cause back pain, poor posture, and skin irritation. Follow these two steps to get the most accurate result from our calculator:
Step 1: Your Band Size
While braless or wearing a non-padded bra, use a measuring tape to measure around your torso directly under your bust, where a bra band would sit. The tape should be level and very snug. If you get a fraction, round to the nearest whole number.
Step 2: Your Bust Size
Measure around the fullest part of your chest (usually at the nipple). Hold the tape somewhat loosely so that it doesn't compress the breast tissue, but ensure it is level all the way around your back.
Understanding Your Results
Bra sizing consists of two parts: the Band (the number) and the Cup (the letter). The cup size is determined by the difference between your bust and your band measurement.
1 inch difference: A Cup
2 inch difference: B Cup
3 inch difference: C Cup
4 inch difference: D Cup
5 inch difference: DD / E Cup
Pro Tip: If the band feels tight but the cups fit perfectly, try a "sister size." A sister size for a 34C would be a 36B (up a band, down a cup) or a 32D (down a band, up a cup).
function calculateBraSize() {
var underbust = parseFloat(document.getElementById('underbust').value);
var bust = parseFloat(document.getElementById('bust').value);
var resultBox = document.getElementById('bra-result-box');
var output = document.getElementById('bra-size-output');
var advice = document.getElementById('bra-advice');
if (isNaN(underbust) || isNaN(bust) || underbust <= 0 || bust <= 0) {
alert("Please enter valid measurements for both fields.");
return;
}
if (bust <= underbust) {
alert("Bust measurement must be larger than underbust measurement.");
return;
}
// Standard "Plus 4" Logic for Band Size
var bandSize;
var roundedUnder = Math.round(underbust);
if (roundedUnder % 2 === 0) {
bandSize = roundedUnder + 4;
} else {
bandSize = roundedUnder + 5;
}
// Cup Logic
var difference = Math.round(bust – bandSize);
var cupLetters = ["AA", "A", "B", "C", "D", "DD/E", "DDD/F", "G", "H", "I", "J", "K", "L"];
var cupResult = "";
if (difference = cupLetters.length) {
cupResult = cupLetters[cupLetters.length – 1];
} else {
cupResult = cupLetters[difference];
}
output.innerHTML = bandSize + cupResult;
resultBox.style.display = 'block';
var adviceText = "Based on a band of " + bandSize + " and a " + difference + "-inch difference.";
if (difference === 0) adviceText = "A very small difference suggests an AA cup.";
advice.innerHTML = adviceText;
resultBox.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}