The Guide to Measuring Bra Size Accurately
Finding the right bra size transforms your daily comfort. A properly fitted bra provides the support your body needs without causing shoulder strain, back pain, or the constant urge to adjust throughout the day.
Most people wear a size that's close but not quite right. Research suggests up to 80% of us could benefit from a size adjustment. Taking fresh measurements gives you a reliable starting point for finding bras that work with your body's unique shape and proportions.
Why Accurate Bra Size Measurements Matter for Your Comfort
The difference between a bra that fits and one that doesn't comes down to precise measurements. Your band provides most of the support, not your straps, so getting this number right directly impacts how supported you feel all day.
Accurate measurements also help you understand sister sizes and make informed choices when shopping different styles. Bodies change over time due to weight fluctuations, hormonal shifts, pregnancy, or even new exercise routines. What fit six months ago might not work today.
When your bra fits properly, you'll notice your clothes drape better. The band sits level across your back, the center gore lies flat against your sternum, and the cups contain your tissue without spillage or gapping. You might even forget you're wearing a bra at all, and that's the goal.
Tools You Need and How to Prepare for Measuring Your Bra Size
Start by gathering a soft measuring tape, the flexible kind used for sewing. No tape on hand? A piece of string or ribbon paired with a ruler works perfectly. Just mark your measurement on the string, then measure it against the ruler.
Wear a non-padded bra when you measure. Padded cups or push-up styles add volume that throws off your numbers; sports bras compress tissue and create equally misleading results. An unlined or lightly lined bra gives you the most accurate baseline.
Stand naturally with your arms relaxed at your sides. A mirror helps you check that the tape stays level all the way around your torso. You can do this solo, though having someone help makes it easier to keep everything aligned.
Step-by-Step Bra Size Measurement Process
Measuring Your Band Size
Wrap the measuring tape around your ribcage directly under your bust, right where your bra band naturally sits. Keep the tape parallel to the floor and snug. You should be able to slip one finger underneath, but not much more.
Determining Your Cup Size
Keep the tape parallel to the floor and wrap it around the fullest part of your bust. This usually sits at nipple level, but follow where you feel fullest as everyone's different.
Let the tape rest gently against your body without compressing or creating indentations. You want an accurate measurement of volume, not how much you can compress.
Calculating Your Bra Size
Enter your band measurement and your bust measurement into our bra size calculator, which will do the math for you. You'll get your best recommended size, plus sister sizes so you can experiment with finding your absolute perfect fit.
Understanding Sister Sizes and When to Use Them
Sister sizes hold the same cup volume but distribute it differently across the band and cup letter. They're your adjustment tool when a bra feels close but not quite right.
The math works like this: go up one band size and down one cup size, or down one band size and up one cup size. A 36C has two sister sizes: 34D (smaller band, larger cup letter) and 38B (larger band, smaller cup letter). All three hold approximately the same volume.
Try the smaller band sister size when your current band rides up in the back or you need more support from the band itself. The 34D would give you a firmer band than the 36C while maintaining similar cup volume.
Go for the larger band sister size if the band feels restrictive but the cups fit well. The 38B provides more room in the band while keeping that cup volume you need.
Sister sizing becomes especially useful when shopping across different brands. Sizing varies between manufacturers. A 34C in one brand might fit like a 36B in another. Knowing your sister sizes means you can adjust on the fly.
Some styles run differently too. A balconette might fit perfectly in your usual size while a plunge bra in the same brand needs a sister size adjustment. This is normal and just part of finding what works for your shape.
Common Bra Size Measurement Mistakes and How to Fix Them
Pulling the tape too tight ranks as the most frequent error. Yes, the band should be snug, but it shouldn't feel like a corset. If you can't comfortably slide two fingers under the band, you've measured too tight or chosen a band that's too small.
Measuring over a heavily padded or sports bra adds several inches to your measurements. This leads to buying cups that are too large for your actual tissue. Always measure in an unlined bra or, if you're between sizes, take measurements both with and without a bra and compare the numbers.
The tape must stay level all the way around your torso. If it rides up in the back or dips in the front, your measurements won't reflect reality. That mirror comes in handy here. Check your tape placement from all angles before recording the number.
Bodies change, yet many people measure once and assume that size stays constant. Weight fluctuations, hormonal shifts, pregnancy, new exercise routines, and simple aging all affect measurements. Check your size every six months or whenever your bras start feeling different.
Rounding incorrectly can throw off your size.
These measurements give you a starting point, not a guarantee. Different styles and brands fit differently. Always pay attention to how a bra actually feels on your body. Comfort and support matter more than the number on the tag.
The right bra should feel supportive and comfortable from the moment you put it on. No breaking-in period required. If something feels off, try a different size or style rather than hoping it will improve with wear.
Now that you know your measurements, we can help you find bras that fit your size. Our wireless designs provide the support you need without the discomfort of underwire, making them ideal for all-day wear.
