How to Measure Bra Size
Learn how to take the two measurements BraFitly uses: your underbust and your bust. Good measurements improve the usefulness of a calculator, but the final fit can still vary by brand and style.
What you need
A soft measuring tape
Use a flexible tape that can sit level around your body. A rigid ruler or a tape that cannot follow the ribcage can introduce errors.
A suitable bra or no bra
A lightly lined or non-padded bra is usually easier than a heavily padded style. If measuring without a bra gives a natural, comfortable position, that can also work.
A mirror
A mirror can help you check that the tape stays horizontal at the front and back.
Step 1: Measure your underbust
Place the tape directly under the bust, around the ribcage. Keep it level and comfortably firm. You should be able to breathe normally. Read the measurement where the tape meets without pulling it painfully tight.
Step 2: Measure your bust
Place the tape around the fullest part of the bust. Keep it level across the back and avoid compressing breast tissue. Stand naturally and breathe normally while taking the reading.
Step 3: Use the same unit
Record both measurements in inches or both in centimetres. BraFitly converts centimetres internally, so you can choose whichever unit is easier for you, but do not mix inches and centimetres in the two input fields.
Step 4: Calculate and interpret the result
BraFitly maps the underbust to an even-inch band starting point and uses the bust-to-band difference to estimate a cup. The result is deliberately presented as a starting point because bra sizing varies between brands and styles.
Common measurement mistakes
- Letting the tape slope upward or downward at the back.
- Pulling the bust tape tightly enough to compress tissue.
- Measuring over a heavily padded bra.
- Holding your breath or changing posture during the measurement.
- Mixing units between the underbust and bust fields.
- Assuming a measurement alone can account for breast shape, cup construction or wire width.
When should you measure again?
Re-measure when your current bra stops fitting comfortably or after meaningful body changes. During pregnancy, postpartum or nursing, current measurements are more useful than automatically returning to an older size.
What the measurement cannot tell you
Two people with the same measurements can prefer different bra shapes. Cup depth, wire width, gore design, fabric stretch and brand grading can change how a bra feels. That is why the calculator should be followed by an actual fit check and the manufacturer's current size chart.
Ready to calculate?
Enter your underbust and bust measurements in the BraFitly calculator.
Open Bra Size Calculator