Calculate Bra Size

Professional Bra Size Calculator

Measure snugly around your ribcage, directly under your bust.

Measure around the fullest part of your chest (usually across the nipple).

Your Estimated Bra Size:

function calculateBraSize() { var underbust = parseFloat(document.getElementById('underbust').value); var bust = parseFloat(document.getElementById('bust').value); var resultContainer = document.getElementById('bra-result-container'); var sizeDisplay = document.getElementById('bra-size-display'); var adviceDisplay = 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 the underbust measurement."); return; } // Calculation Logic (Standard US/UK Industry Method) // Determine Band Size: If underbust is even, add 4. If odd, add 5. var band; if (Math.round(underbust) % 2 === 0) { band = Math.round(underbust) + 4; } else { band = Math.round(underbust) + 5; } // Determine Cup Size based on the difference between Bust and calculated Band var diff = Math.round(bust – band); var cup = ""; var cupMapping = { 0: "AA", 1: "A", 2: "B", 3: "C", 4: "D", 5: "DD (E)", 6: "DDD (F)", 7: "G", 8: "H", 9: "I", 10: "J" }; if (diff 10) { cup = "K+"; } else { cup = cupMapping[diff]; } sizeDisplay.innerHTML = band + cup; adviceDisplay.innerHTML = "Remember: This is a starting point. Different brands and styles (like balconette vs. plunge) may fit differently. Always try on a 'sister size' if the band feels right but the cup gapes (go down a cup) or spills (go up a cup)."; resultContainer.style.display = 'block'; }

Finding the right bra size is more than just a matter of comfort; it is essential for posture, confidence, and garment aesthetics. Statistics suggest that nearly 80% of women are wearing the wrong bra size, often settling for a band that is too large and cups that are too small. Our calculator uses the industry-standard measurement method to provide you with a reliable starting point.

Step-by-Step Guide to Measuring Yourself

To get the most accurate results from the bra size calculator, you will need a soft measuring tape and should ideally measure while braless or wearing a very thin, non-padded bra.

• Measure Your Underbust: Wrap the tape measure around your ribcage directly under your breasts. Keep the tape level and pull it snug (but not so tight that it cuts into your skin). Round this number to the nearest whole inch.
• Measure Your Bust: Wrap the tape around the fullest part of your chest. Do not pull the tape tight here; it should rest gently against your skin without compressing the breast tissue. Ensure the tape is level across your back.

Understanding the Math Behind the Size

The bra size consists of two parts: the Band Size (the number) and the Cup Size (the letter). In traditional sizing logic, the band size is adjusted from your raw underbust measurement to ensure the elastic provides enough tension to support the weight of the breasts. The cup size is then determined by the volume difference between your band and your full bust.

Difference (Bust – Band)	Cup Size
Less than 1 inch	AA
1 inch	A
2 inches	B
3 inches	C
4 inches	D
5 inches	DD (E)

Signs Your Current Bra Doesn't Fit

If you experience any of the following, it's time to use our calculator and update your wardrobe:

• The Band Rides Up: If the back of your bra sits higher than the front, the band is too large and not providing support.
• Spillage (The "Quadra-boob"): If your breast tissue spills over the top or sides of the cups, you need to go up at least one cup size.
• Gapping: If there is space between your breast and the cup, you may need a smaller cup or a different cup shape.
• Slipping Straps: Frequently slipping straps are often a sign that the band is too large; the straps are set too wide for your frame because the band is not anchored properly.

The Concept of Sister Sizes

If the calculator gives you a size like 34C, but you find the band is too tight while the cup volume feels right, you should try a Sister Size. A sister size maintains the same cup volume but changes the band. To go up a band size, you must go down a cup letter (e.g., 34C is the same volume as 36B). Conversely, to go down a band size, go up a cup letter (e.g., 34C is the same volume as 32D).