How to Measure Bra Size at Home
To measure your bra size, wrap a soft tape snugly around your ribcage under your bust for the band, then loosely around the fullest part of your bust, standing, leaning forward and lying down. Round the band to an even inch; each inch of difference to the bust is one cup letter.
Step by step
Get ready
Use a soft measuring tape. Wear a non-padded bra or no bra, stand straight and breathe out normally. A mirror helps you keep the tape level.
Measure the band
Wrap the tape around your ribcage directly under your bust. Pull it snug, keep it level all the way round, and read the number. This is your snug underbust.
Optional: relaxed underbust
Measure the same place again with the tape just touching your skin. If it is much bigger than the snug number, you may prefer a sister size with a larger band.
Measure the bust standing
Wrap the tape around the fullest part of your bust. Keep it level across your back and loose enough that it does not press in.
Measure leaning forward
Bend forward at the hips until your upper body is level with the floor, then measure the fullest part again. This often gives the most useful number for soft or full busts.
Measure lying down
Lie on your back and measure around the fullest part once more. Enter all the bust numbers you have; the calculator averages them.
Work out your size
Round the snug underbust to the nearest even inch for the band. Subtract the band from the bust average. Each inch of difference is one cup letter.
Enter your measurements
The calculator needs JavaScript. Without it, use the steps and the size chart below: measure your snug underbust and your bust in inches, round the underbust to the nearest even number for the band, and count one cup letter per inch of difference.
Calculated in your browser. Your last measurements are kept only on this device until you press Clear.
Your starting size
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Sizes vary between brands and styles. Use this as a starting point and try bras on: the band should sit level and feel firm on the loosest hook.
Next: sister sizes explained · convert to other countries · measuring tips
Common measuring mistakes
- The tape slopes up at the back. Check in a mirror that it is level all the way round.
- Measuring over a padded bra. Padding adds to the bust number.
- Pulling the bust tape tight. The bust tape should rest on the body without pressing in.
- Holding your breath. Breathe out normally before reading the band.
- Adding inches to the band. The older "plus four" method is not used here; see below.
About the "plus four" method
This site uses the tape method followed by most current fitting guides: the band is your snug underbust in inches, rounded to the nearest even number, and the cup is the difference between your bust and that band, one letter per inch. Some older guides tell you to add 4 or 5 inches to the underbust for the band. Most modern guides no longer do this, and it tends to give a looser band and smaller cup. If you are used to that method, your result here may show a smaller band and larger cup letter than you expect.
Printing this guide
Use your browser’s print command. Menus and buttons are left out on paper so the steps and drawings fit on the page.
No measuring tape?
Use a piece of string or a phone charging cable and a ruler, or print the paper tape on our measuring without a tape page.
Frequently asked questions
How do I measure my bra size at home?
You need a soft tape measure. Measure snugly around your ribcage under your bust for the band, then loosely around the fullest part of your bust. Enter both in the calculator, or round the band to an even inch and count one cup per inch of difference.
Should I wear a bra while measuring?
Wear a non-padded, well-fitting bra or no bra. A padded or push-up bra adds to the bust measurement and makes the cup look bigger than it is. A very worn-out bra can make it look smaller.
How tight should the tape be for the band?
Snug and level: firm enough that it does not slide down, but you can still breathe normally. Read the number after breathing out. If the snug and relaxed numbers are very different, try both band sizes.
What if my band measurement is an odd number?
Round to the nearest even number. With the tape method on this site, 31 inches usually becomes a 32 band and 29 becomes 30. If you are right between, try both and choose the one that feels firm without digging in.
Why measure leaning forward?
Leaning forward lets breast tissue fall away from the chest so the tape catches all of it. For soft, full or wide-set busts this often gives a larger and more realistic bust number than standing.
How often should I measure?
Measure again whenever a bra stops fitting well, and after changes such as weight change, a new training routine, pregnancy or nursing. Many people simply check once or twice a year.
Last updated: October 15, 2026