Quick Answer

To measure your bra size at home, you'll need a soft measuring tape. Measure your band size by wrapping the tape snugly around your ribcage, just under your bust. Then measure your bust at the fullest part. Subtract the band measurement from the bust measurement to find your cup size using a simple chart.

Finding a well-fitting bra can feel like a treasure hunt, but you don't need a professional fitting to get it right. With a soft measuring tape and a few minutes, you can measure your bra size at home and finally understand what those numbers and letters mean.

Whether you're shopping online or in stores, knowing your measurements helps you narrow down options and avoid the frustration of ordering the wrong size. Here's a straightforward way to get accurate numbers every time.

What You'll Need

Before you start, grab a soft measuring tape (the kind used for sewing). If you don't have one, a piece of string and a ruler can work in a pinch. Wear a non-padded bra or no bra at all to get the most accurate bust measurement.

Stand in front of a mirror with your arms relaxed at your sides. It helps to have someone else take the measurements, but you can do it solo with a little practice.

  • Use a cloth measuring tape, not a metal one.
  • Keep the tape level and parallel to the floor.
  • Measure twice to confirm consistency.

Step 1: Measure Your Band Size

Wrap the tape around your ribcage, right under your bust. It should be snug but not digging into your skin. Make sure the tape is level all the way around. Take a deep breath and note the measurement in inches.

If the number is even, add 4 inches. If it's odd, add 5. This gives you your band size. For example, a 30-inch underbust measurement typically corresponds to a 34 band size.

  • Common mistake: pulling the tape too tight, which results in a smaller band size than you need.
  • Checkpoint: You should be able to slide one finger comfortably under the tape.

Step 2: Measure Your Bust Size

Wrap the tape around the fullest part of your bust, keeping it level and parallel to the floor. Don't pull it tight—let it rest naturally against your skin. Note this measurement in inches.

This number is your bust size. It's best to measure without a padded bra so you're not adding extra bulk that could skew the result.

  • Common mistake: measuring over a heavily padded bra, which inflates the number.
  • Checkpoint: The tape should not cause any indentation in your skin.

Step 3: Calculate Your Cup Size

Subtract your band size from your bust measurement. The difference determines your cup size: 1 inch = A, 2 inches = B, 3 inches = C, 4 inches = D, and so on. For example, if your band size is 34 and your bust is 36, the difference is 2, making you a B cup.

Combine your band size and cup size to get your full bra size, like 34B. Keep in mind that sizing varies between brands, so treat this as a starting point.

  • Common mistake: forgetting that cup size is relative to band size—a 32C is not the same volume as a 36C.
  • Checkpoint: If you're between sizes, try the sister size (e.g., 34B and 32C have the same cup volume).

Step 4: Try It On (or Use a Calculator)

Once you have your numbers, you can use an online bra size calculator to double-check. But the real test is how it feels. A well-fitting bra should have a snug band that stays level, straps that don't dig, and a center gore that lies flat against your sternum.

If you're shopping online, look for stores that offer detailed size guides or flexible return policies. Many brands, including Thistle and Spire, provide fit notes on their product pages to help you choose.

  • Common mistake: relying only on the calculator without considering brand differences.
  • Checkpoint: The band should provide about 80% of the support, not the straps.

Step-by-Step Recap

  1. Measure your band: Wrap the tape under your bust, snug but not tight. Add 4 if even, 5 if odd. Checkpoint: One finger should fit under the tape.
  2. Measure your bust: Wrap the tape around the fullest part, keeping it level and not too tight. Checkpoint: The tape shouldn't leave marks.
  3. Calculate your cup: Subtract band from bust; 1 inch = A, 2 = B, etc. Checkpoint: Try sister sizes if between.
  4. Test the fit: Use a calculator or try on bras, checking band level and strap comfort. Checkpoint: The band should do the heavy lifting.

Products That Fit Your Measurements

  • Mullberry Keyhole Bralette: Floral embroidered keyhole V-wire bralette with racerback straps. Adjustable at center back hooks and straps. Adjustable straps and back hooks let you fine-tune the fit, which is helpful if you're between sizes.
  • Medusa Set - Toffee: Tulle, front closure styled sheer bralette with our iconic T&S serpentine embroidery and finished into a mesh back. Adjustable at shoulder and back straps. Front closure and adjustable straps make it easier to put on and customize, ideal for those who prefer a more tailored fit.

Measuring your bra size at home is a simple skill that pays off every time you shop. Remember that sizing can vary between brands, so always check the specific size guide and be open to trying different styles. With these steps, you'll be well on your way to finding bras that feel as good as they look.