We’re often taught by lingerie behemoths that bra size measurements should be left to the professionals—which would explain why many of us have gone our whole lives relying on others to tell us what size bra we should be wearing. This is all fine, except that many women get stuck in a rut of wearing the same bra size for years and years, assuming things like, “I’m a 34B; I always have been and always will be.”
This kind of thinking can get you into trouble fast, since (obviously) your bra size changes as your body does. And since you probably don’t want to go careening to and from Victoria’s Secret every time your body changes, it’s probably worth it for all of us—and I mean all of us—to learn how to measure our bra size at home.
Below, find a quick and dirty five-step guide to measuring your bra size at home.
1. Grab a Tape Measure
Make sure it’s soft and pliable, preferably made of fabric. If you don’t have one, head to a local fabric store, drug store or even a mass retailer, like Walmart.
2. Make Sure You’re Wearing Your Best Bra
You wouldn’t go on a first date without first putting on your best outfit, so don’t measure your bra size without wearing your most well-fitting bra. It should fit snugly, preferably have an underwire and be sans padding.
Pro tip: Be sure your breasts aren’t sagging; if your nipple isn’t located approximately halfway down the top half of your back, adjust your bra straps to make them tighter.
3. Measure Your Band Size First
As you know, most bras are sized via band then cup., i.e., a 34-D bra is a bra with a band measurement of 34 and a cup measurement of D. But don’t be fooled by appearances: The band size often isn’t precisely the measurement of the circumference of your torso.
Here’s how it works: Using your soft tape measure, measure around the trunk of your torso right where the bottom part of your bra clasps around you. Using a mirror, make sure the tape is taut exactly across the middle of your back (not hitting at a diagonal, which can skew the measurement). See where the end of the tape meets at the front of your torso. This is your literal torso measurement. Write this number down.
Sometimes, your band size is equivalent to your literal torso measurement. But if your torso measures, for example, 31 inches, you will probably need to round up to a 32 for your band size.
4. On to Measuring Your Bust Size
Compared to measuring bust size, band size is a relative walk in the park. Cups are trickier because the size of your breasts can actually change depending on myriad factors, like what day of the month it is and if you are experiencing bloating or not. Try to pick a day to measure your cup size when you feel (relatively) true-to-size.
Your posture also plays an important part in measuring an accurate cup size. To counteract a mis-measurement on account of slouching or standing up abnormally erect, try this: Bend forward at your hips before measuring. So your body, from your feet to the top of your head, looks like an upside-down letter “L.”
This helps ensure that you are getting all the breast tissue in the tape. Then carefully place the tape so it’s straight across your back (again, you can use a mirror to help you do this) and measure your breasts at the fullest point, which typically is where your nipples are. Take a mental (or literal) note of that number.
5. Calculate the Cup Size
Because in the land of bras, everything is more confusing than it really needs to be: Your bust size and your cup size aren’t the same. The bust size is the literal number you just read on the tape measure while contorting yourself into the “L” shape. The cup size, however, is the difference between your band size and your bust size.
Here’s a chart of standard size differences and how they equate to cup sizes:
- If your bust size is less than 1 inch bigger than your band size, you’re a cup size AA.
- 1-inch difference = A
- 2-inch difference = B
- 3-inch difference = C
- 4-inch difference = D
- 5-inch difference = DD
- 6-inch difference = DDD or F
- 7-inch difference = DDDD or G
- 8-inch difference= H
- 9-inch difference = I
- 10-inch difference = J
- 11-inch difference = K
- 12-inch difference = L
- 13-inch difference = M
- 14-inch difference = N
- 15-inch difference = O
Here’s an example from start to finish:
Let’s say you measure around your torso and get the measurement of 33 inches. Because it’s an odd number, you should round up to 34. When you measure around your full bust, you get 36 inches. That means there’s a 2-inch difference between your full bust size and your band size. The chart above says a 2-inch difference is equivalent to a “B” cup size, so your final bra size is: 34B.
Make sense? There’s also this handy-dandy bra size calculator if you’re still feeling a bit lost.
A version of this article was originally published in December 2013.