Bra Size Calculator
Use a soft measuring tape and enter your measurements to get a starting bra size.
Tip: Measure while standing naturally and keeping the tape level around your body.
How to check your bra size at home
Finding your bra size is easier than most people think. You only need two measurements: your underbust and your fullest bust. This calculator gives you a practical starting size so you can shop with more confidence and reduce returns.
Remember: bra sizing is not perfectly standardized across every brand. Think of your calculator result as your baseline size, then fine-tune based on style, brand, and personal comfort.
Step 1: Measure your underbust
Wrap a soft measuring tape directly under your bust, around your ribcage. Keep the tape parallel to the floor and snug (not painfully tight). This measurement is used to estimate your band size.
Step 2: Measure your fullest bust
Measure around the fullest part of your bust, usually across the nipples, with the tape level all the way around. Keep the tape gently resting on the body without compressing tissue.
How this calculator works
- Band size is estimated by rounding your underbust to the nearest even number.
- Cup size is estimated from the difference between bust measurement and band size.
- Each inch of difference generally increases cup size by one step (A, B, C, D, and beyond).
This is a common modern approach and works well for many people. If your result feels close but not perfect, try a neighboring “sister size” too.
Bra fit checklist
After you get your calculator result, use this checklist when trying on bras:
- Band: should feel firm and level around your torso, not riding up the back.
- Straps: should stay in place without digging into your shoulders.
- Cups: no gaping at the top and no spilling over the edges.
- Center gore: in underwire bras, should lie close to the sternum.
- Comfort: no pinching, rubbing, or pressure points after several minutes.
Understanding sister sizes
Sister sizes keep cup volume similar while changing band tightness. If your band is too tight, go up one band size and down one cup letter. If your band is too loose, go down one band size and up one cup letter.
Example: if 34C feels tight in the band, try 36B. If 34C feels loose in the band, try 32D.
Common mistakes when checking bra size
- Measuring over thick clothing instead of directly on the body.
- Holding the tape at an angle instead of level.
- Using an old stretched tape measure.
- Choosing cup size only by letter without considering band size.
Final notes
Your body can change over time due to weight shifts, hormonal cycles, pregnancy, training, or age. Re-check your bra size every 6 to 12 months for best comfort and support.
This calculator is for general guidance and everyday shopping convenience. For complex fit needs, post-surgery fittings, or persistent discomfort, a professional in-person fitting can be very helpful.