How to Measure Yourself for a Bra at Home: A Simple Step-by-Step Method

Quick answer

To measure your bra size at home, wear an unpadded bra or no bra, wrap a soft tape snugly around your ribcage directly under your bust, and round to the nearest even number for your band size. Then measure around the fullest part of your bust, subtract the band from the bust, and use the difference to find your cup size. For AA, A, and B cups, a 0–1 inch difference is an AA, 1–2 inches is an A, 2–3 inches is a B, and so on.

A bra that fits starts with two numbers: your band and your cup. Most fitting problems, from straps that slip to cups that gap, trace back to measuring one of those incorrectly or skipping a step. You can get a reliable starting point at home in about five minutes with a soft measuring tape and a mirror.

This method is designed for small busts, including AA, A, and B cups, where standard calculators sometimes round you into a size that feels too big. Use it as a baseline, then check the fit against real bras you own. If you are between sizes, the band measurement matters most because it carries about 80 percent of the bra's support.

What you need before you start

Gather a soft, flexible measuring tape (the kind used for sewing), a mirror, and a piece of paper or your phone to record numbers. If you do not have a soft tape, use a piece of string or a ribbon, then lay it flat against a ruler. A rigid tape measure, like the kind for home repair, will not follow your body's curves and will give you a false reading.

Wear an unpadded, non-molded bra, or go without one. A padded or push-up bra adds volume that is not yours, which inflates your cup measurement. If you only own padded bras, take them off for the bust measurement. The mirror helps you keep the tape level around your back, which is the single most common source of wrong numbers.

• Do not measure over thick clothing or a sweatshirt; a thin T-shirt is fine if you prefer not to measure against skin.
• Stand tall and breathe normally. Do not inhale and hold your breath, which expands your ribcage and adds inches.

Step 1: Measure your band size

Wrap the tape around your ribcage, directly under your bust, where the bra band sits. Keep the tape snug and level all the way around, parallel to the floor. Check in the mirror that the back of the tape is not riding up. Exhale normally and read the number where the tape meets in front.

If the number is even, that is your band size. If it is odd, round down to the nearest even number for a snugger band, or up for a looser one. Most people find rounding down gives better support. Write this number down; it is the foundation for everything else.

• Common mistake: letting the tape sag in the back. A sagging tape makes your band measurement too large, which leads to a band that rides up.
• Checkpoint: the tape should feel snug but not painful. You should be able to fit one finger under it.

Step 2: Measure your bust size

Wrap the tape around the fullest part of your bust, usually across the nipple line. Keep the tape level and relaxed, not tight. Do not pull it snug like the band measurement; you want the tape to rest gently against your bust without compressing any tissue. Arms should be down at your sides.

Read the number at the front where the tape meets. If you are wearing an unpadded bra, measure over it. If you are not wearing a bra, make sure your bust is in its natural position, not lifted or pushed together. Record this number.

• Common mistake: pulling the tape too tight across the bust. This compresses the tissue and gives a cup size that is too small.
• Checkpoint: the tape should touch your bust all the way around but not indent the skin.

Step 3: Calculate your cup size

Subtract your band measurement from your bust measurement. The difference in inches tells you your cup size. A 0 to 1 inch difference is an AA cup, 1 to 2 inches is an A cup, 2 to 3 inches is a B cup, 3 to 4 inches is a C cup, and so on. For example, if your band is 32 and your bust is 34, the difference is 2 inches, which is a B cup.

If your difference falls right on the line between two cup sizes, try both. Small-bust sizes often run slightly differently between brands, so your true size may be one or the other depending on the bra's cut. This is especially common for AA and A cups, where a half-inch can change the fit.

• Common mistake: using a bra size calculator that adds 4 or 5 inches to your band. That old method pushes small busts into bands that are too loose and cups that are too big.
• Checkpoint: if your calculated cup size seems too large, remeasure your band. A band that is too loose will make the difference look bigger than it is.

Step 4: Test the size against a real bra

Numbers give you a starting point, but the fit test is what confirms it. Put on a bra in your calculated size and check the band first. It should sit level and snug around your ribcage, not ride up when you lift your arms. Then check the cups: the center gore should lie flat against your sternum, and the underwire (if present) should sit on your ribcage, not on breast tissue.

For small busts, pay attention to whether the cups gap at the top or wrinkle. If they do, you may need a smaller cup or a different style, such as a bralette or a lightly lined bra. If the band feels tight but the cups fit, try a band size up with a cup size down (sister sizing).

• Common mistake: assuming a gap means you need a bigger cup. In small sizes, gapping usually means the cup is too big or the shape is wrong for you.
• Checkpoint: the band should stay in place when you raise your arms. If it slides up, go down a band size.

Step 5: Adjust for common small-bust fit issues

Small busts often need a different approach than the standard measuring guide suggests. If you measure as an AA or A but find that most bras in that size still gap, look for styles designed for close-set or wide-set breasts, which change how the cups sit. Wire-free and lightly contoured bras can also create a smoother line without empty space.

If your band size is 32 or smaller, you may find that some brands do not carry your size. In that case, your at-home measurement is even more important because you will likely need to shop from brands that specialize in small bands and small cups. Recheck your measurements every six months or after any weight change.

• Common mistake: settling for a band that is too big because the cup size is easier to find. A loose band will not support you and will make the cups feel wrong.
• Checkpoint: if you are between band sizes, choose the smaller band and use an extender if needed. The band will stretch over time.

Your at-home measuring steps at a glance

1. Prepare: Wear an unpadded bra or no bra. Stand in front of a mirror with a soft tape and something to record numbers. Checkpoint: no padded or push-up bras for this measurement.
2. Measure band: Wrap the tape snugly around your ribcage directly under your bust, level all the way around. Round to the nearest even number. Common mistake: letting the tape sag in back. It should be snug, not tight.
3. Measure bust: Wrap the tape around the fullest part of your bust, keeping it level and relaxed. Do not pull tight. Common mistake: compressing the bust, which gives a too-small cup.
4. Calculate cup: Subtract band from bust. 0–1 inch = AA, 1–2 = A, 2–3 = B, 3–4 = C. Common mistake: using a calculator that adds inches to your band.
5. Fit test: Try a bra in your calculated size. Band should be level and snug; cups should not gap or wrinkle. Checkpoint: if the band rides up, go down a band size.
6. Adjust for small bust: If cups gap, try a smaller cup or a style made for your shape, such as a bralette or lightly lined bra. Next step: recheck measurements every six months.

Styles that work with your measurements

• Hattie: Hattie combines the comfort of a bralette with enough coverage to create natural shape and cleavage. Inspired by our popular Jamie bra, Hattie features soft, satiny microfiber for a smooth silhouette and a deep-plunge neckline that flatters the décolletage. An extra-wide striped elastic underband creates a longline look with firm, comfortable support. If your measurements put you in a small band and cup, Hattie's wide underband gives you the support of a bra without the gaping cups that can happen with traditional styles.



• Joanna: Joanna combines wire-free comfort with a smooth, natural-looking shape. Lightly lined molded cups create a seamless silhouette beneath T-shirts, while interior mesh panels provide gentle lift without added padding. Full coverage makes this an effortless choice for everyday wear. Joanna's molded cups are a good test for your calculated size because they show gaps or wrinkles clearly. If it fits smoothly, your measurement is likely accurate.
• Danielle: Danielle is a lace bralette designed to create natural shape without an underwire. Lightly contoured cups and interior mesh panels provide gentle lift and support, while brightly colored lace adds a feminine finish for any occasion. Danielle is a useful check for AA and A cups because its wire-free design relies on the band for support. If the band fits from your measurement, this bralette will stay in place.

Measuring yourself at home is not about chasing a perfect number. It is about finding a starting size that gets you close, then using the fit test to fine-tune. Once you know your band and cup, you can shop with confidence and skip the sizes that were never going to work.