Bra Size Calculator to Find Your Perfect Fit Instantly

Finding the right bra size can feel like guesswork, especially since sizing shifts so much from one brand to the next. The Bra Size Calculator cuts through that confusion, giving you a fast, reliable estimate of your band and cup size from just two measurements. Here's how to work through it, step by step.

Step 1: Prepare for an Accurate Measurement

Before you pick up the tape, put on a bra without padding — something that fits reasonably well and isn't heavily lined or a push-up style. Padding and underwire shaping tend to skew the numbers, so a soft, simple bra will give you the truest read.

Grab a soft measuring tape, the sewing kind, and stand naturally in front of a mirror. The tape should sit snug against your body without digging in or leaving marks.

Step 2: Measure Your Underbust (Ribcage)

Wrap the tape directly under your bust, around your ribcage, making sure it stays level and parallel to the floor. Breathe normally and read the number in inches once you've settled.

That number goes into the "Underbust (Ribcage)" field — it's the foundation your band size is built on.

Step 3: Measure Your Bust (Fullest Part)

Now wrap the tape around the fullest part of your bust, usually right at nipple level, keeping it level the whole way around. Let it rest comfortably rather than pulling it tight, since that's what gives you an accurate reading.

Enter that number into the "Bust (Fullest Part)" field.

Step 4: Calculate Your Size

With both measurements entered, click "Calculate Size" and you'll immediately get a suggested size pairing a band number with a cup letter, something like "34B" or "36DD." Behind the scenes, the band comes straight from your underbust measurement, while the cup size is worked out from the gap between your bust and band numbers — the wider that gap, the larger the cup, scaling from AA at the small end up through G and beyond as the difference grows.

Step 5: Try It On and Adjust

The calculator gives you a solid starting point, but keep in mind that fit still shifts between brands, styles, and even fabrics. Treat your calculated size as a baseline for shopping, and try the bra on whenever you can. A few signs a bra actually fits: the band sits level and snug around your ribcage without riding up in back, the center gore lies flat against your sternum, the cups fully contain your bust with no gaps or spillage, and the straps stay put without cutting into your shoulders. If anything feels off, go up or down a size in the band or cup without hesitation — comfort and support are what really decide the fit.

Why Accurate Sizing Matters

The wrong bra size does more than feel uncomfortable — it can throw off your posture, lead to back and shoulder pain, and make clothes sit wrong. Get the fit right, though, and you gain better support, a smoother line under clothing, and comfort that lasts through the day.

The Bra Size Calculator takes the guesswork out of the equation, whether you're shopping online, trying a brand for the first time, or it's just been a while since you were last measured. Bodies change with time, weight shifts, and pregnancy, so it's worth re-measuring every so often to make sure the size you're wearing still matches the size you actually are. Two quick measurements are all it takes to walk into your next bra shopping trip with a real starting point — because comfort that lasts all day starts with getting the fit right.