How to Measure Your Bra Size at Home
Finding your ideal bra size starts with taking two basic measurements: your underbust (band) and your full bust. Using a soft fabric measuring tape, follow these four simple steps to establish your baseline size.
Step 1: Measure Your Underbust (Band Size)
Stand upright with your arms relaxed at your sides. Wrap the measuring tape snugly around your ribcage, directly beneath your bust where your bra band sits.
- Tape position: Keep the tape level across your back, parallel to the floor.
- Tension: Pull the tape snug against your ribcage without compressing your lungs.
- Posture: Exhale normally and relax your shoulders while reading the number.
Figure 1: Correct level underbust placementStep 2: Measure Your Bust Size
Wrap the measuring tape loosely around the fullest part of your bust (usually across the nipples).
- Tape position: Ensure the tape remains level across your back without drooping.
- Tension: The tape should rest lightly against your skin without indenting or squishing your bust.
- Posture: Stand naturally without holding your breath or arching your chest forward.
Figure 2: Correct loose bust placementEnter Your Measurements into the Calculator
Ready with your numbers? Input your underbust and bust measurements for an instant starting size.
Step 4: Understand Your Results
Once calculated, your baseline bra size provides four important pieces of information:
1. Baseline Band & Cup
Your recommended starting size (e.g. 34C in US/CA sizing).
2. Sister Sizes
Equivalent cup volumes with tighter or looser band options (Sister Size Tool).
3. International Equivalents
Equivalent size labels for UK, EU, FR, AU, and JP (Converter Tool).
4. Fit Adjustments
Diagnostic checks for band riding up or cup gaping (Fit Guide).
7 Common Measurement Mistakes to Avoid
1. Measuring over thick clothing
Always measure over bare skin or a thin, non-padded unlined bra to avoid adding extra inches.
2. Measuring tape sagging at the back
Check in a mirror to ensure the tape remains strictly level and parallel to the floor all around.
3. Pulling the bust tape too tight
The bust measurement tape must rest lightly against your skin without flattening tissue.
4. Holding your breath
Inhale and exhale normally so your ribcage is at its natural baseline size when reading the band number.
5. Mixing up inches and centimeters
Double-check your measuring tape units (`in` vs `cm`) before selecting the unit toggle in the calculator.
6. Swapping underbust and bust inputs
Make sure your smaller underbust number goes into Step 2 and your larger bust number goes into Step 3.
Visual Measurement Comparison
Tape Level vs Sagging
Incorrect: Sagging Tape
Incorrect: Squishing BustFrequently Asked Questions
Should I measure with a bra on?↓
Yes, ideally measure while wearing an unpadded, non-push-up bra that holds your bust in a natural position without compressing tissue. If you don't have one, measuring on bare skin is also fine.
Should the tape be pulled tight?↓
The tape should be snug around your underbust (ribcage) so the band provides proper support, but loose and light around your bust so tissue isn't squished.
What if I am between band sizes?↓
If your underbust measurement falls on an odd number (such as 31 or 33 inches), round up to the nearest even number (32 or 34) and check both your baseline and sister sizes. Read our full guide on What To Do If You're Between Bra Sizes.
Why does my calculated size differ from my current bra?↓
Many people wear bra bands that are too loose or cups that are too small due to outdated sizing rules (+4 method). Your calculated size establishes a true modern baseline. Read How Often Should You Recheck Your Bra Size? to keep your baseline accurate.