How to Measure Your Bra Size at Home: Step-by-Step

Quick answer

Measure your band snugly around your ribcage, then measure your bust at the fullest point. Subtract band from bust to get your cup size. Always measure over a thin, unlined bra, keep the tape level, and round to the nearest half-inch. If you're between sizes, sister-size up or down as needed.

What you'll need before you start

A soft measuring tape, a mirror, and a thin, unlined bra are essential. Avoid padded or push-up bras because they distort your bust measurement. If you don't have a soft tape, use a string and a ruler. Stand in front of a mirror to keep the tape level. Write down every measurement as you go. This bra size measurement guide assumes you're measuring yourself, but a friend can help for the bust step.

• Soft measuring tape or string + ruler
• Mirror (full-length if possible)
• Thin, unlined bra (no padding)
• Pen and paper or notes app

Step 1: Measure your band size

Wrap the tape around your ribcage, directly under your bust. The tape should be snug but not digging in. Keep it parallel to the floor. Breathe normally and exhale before reading the number. If the measurement is an even number, add 4 inches; if odd, add 5 inches. This gives your band size in inches. For example, a 31-inch ribcage becomes a 36 band. Common mistake: pulling the tape too tight or letting it ride up in the back. Check in the mirror that the tape is level all the way around.

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 not too tight. Don't compress breast tissue. Stand straight with arms at your sides. Round to the nearest half-inch. Common mistake: measuring over a padded bra or pulling the tape so tight it flattens your bust. If your breasts are asymmetrical, measure the fuller side and use that number. Write this number down.

Step 3: Calculate your cup size

Subtract your band measurement (the number before adding 4 or 5) from your bust measurement. The difference determines your cup size. Use this standard chart: 0 inches = AA, 1 inch = A, 2 inches = B, 3 inches = C, 4 inches = D, 5 inches = DD/E, 6 inches = DDD/F, 7 inches = G. If you're between cup sizes, try both. Common mistake: using the band size after adding 4 or 5 instead of the original ribcage measurement. That throws off the math.

Step 4: Find your sister sizes

If your calculated size feels off, sister sizing can help. Sister sizes have the same cup volume but different band lengths. To go down a band, add a cup letter; to go up a band, subtract a cup letter. For example, if you measure 34C, your sister sizes are 32D and 36B. This is useful when a band feels too tight or too loose. Common mistake: assuming sister sizes always fit the same. The cup volume is similar, but the band will feel different. Always try before you buy if possible.

Step 5: Confirm your fit at home

Put on your best-fitting bra and check these points: the band should be snug and level, not riding up. The center gore should lie flat against your sternum. Cups should contain all breast tissue without spilling or gaping. Straps should be adjusted so you can fit one finger under them. If the band rides up, go down a band size and up a cup. If cups gape, go down a cup size. If you spill over, go up a cup. Common mistake: ignoring band fit because the cups seem fine. The band provides 80% of support, so it must be right.

Your at-home measuring steps

1. Measure band: Wrap tape snugly around ribcage, under bust. Add 4 inches if even, 5 if odd. Checkpoint: tape should be level and comfortable.
2. Measure bust: Wrap tape around fullest part of bust, keep level, round to nearest half-inch. Checkpoint: don't compress breast tissue.
3. Calculate cup: Subtract band (before adding 4/5) from bust. Use difference to find cup size. Checkpoint: 1 inch = A, 2 = B, 3 = C, etc.
4. Find sister sizes: Adjust band up/down and cup letter inversely to find alternate sizes. Checkpoint: try both sizes if you're between.
5. Confirm fit: Check band level, gore flat, cups smooth, straps snug. Checkpoint: band should not ride up.

Product facts

• Luz Black Demi Bra: Embroidered black French tulle demi cup and Italian stretch tulle back. Adjustable grosgrain straps and decorative picot elastic trim. The demi cup shape works well for rounded necklines, and the adjustable straps let you fine-tune the fit after measuring.
• Camille Demi: Demi silhouette with underwire provides flattering lift. Features pinstripe scalloped lace and a sheer tulle sling for added structure. Fully adjustable grosbeak elastic straps. The underwire and sling offer extra support, which can be helpful if you're between sizes and need a more secure fit.