How to Measure Your Bra Size at Home
Finding the right bra size is essential for comfort, posture, and confidence. Measurements can change due to weight fluctuation, aging, or pregnancy, so we recommend measuring yourself every 6 months. Follow these simple steps using a soft measuring tape.
Step 1: Measure Your Band Size (Underbust)
Stand in front of a mirror wearing a non-padded bra or no bra. Wrap the measuring tape around your ribcage, directly underneath your bust. Ensure the tape is snug and parallel to the ground.
- If you get an even number (e.g., 32), that is your potential band size.
- If you get an odd number (e.g., 33), round up to the next even number (e.g., 34).
- Note: Some brands use the "+4 method" (adding 4 inches to your measurement), but modern fitting guides suggest wearing a band closer to your actual ribcage measurement for better support.
Step 2: Measure Your Cup Size (Overbust)
Wrap the tape around the fullest part of your bust (usually at nipple level). This measurement should be loose enough that it doesn't dig into your breast tissue, but tight enough to stay in place.
Step 3: Calculate the Difference
Subtract your Band size from your Bust size. The difference in inches tells you your cup size:
| Difference (Inches) | Cup Size | Example |
|---|---|---|
| 0 - 0.5" | AA | 34" Bust - 34" Band |
| 1" | A | 35" Bust - 34" Band |
| 2" | B | 36" Bust - 34" Band |
| 3" | C | 37" Bust - 34" Band |
| 4" | D | 38" Bust - 34" Band |
| 5" | DD (E) | 39" Bust - 34" Band |
| 6" | DDD (F) | 40" Bust - 34" Band |
What are "Sister Sizes"?
If your calculated size doesn't feel quite right, try a Sister Size. Sister sizes are bra sizes that have the same cup volume but different band lengths.
The Rule: If you go UP a band size, go DOWN a cup size. If you go DOWN a band size, go UP a cup size.
- Original: 34C
- Sister Size (Looser Band): 36B
- Sister Size (Tighter Band): 32D
Signs You Are Wearing the Wrong Bra
Even if the calculator gives you a number, the true test is how it feels. Look out for these red flags:
- Straps Digging In: This usually means the band is too loose, forcing the straps to carry all the weight. Try a smaller band size.
- Band Riding Up the Back: The back of your bra should sit level with the front. If it arches up, the band is too big.
- Cup Gaping: If there is empty space at the top of the cup, try going down a cup size or switching to a "balconette" style.
- Quad-Boob (Spilling Over): If your breasts are spilling out over the top or sides, the cup is too small. Go up a cup size.
Frequently Asked Questions (FAQ)
Are US and UK bra sizes the same?
They are the same up to a D cup. After that, they diverge. US sizing usually goes D, DD, DDD, G, H. UK sizing goes D, DD, E, F, FF, G, GG. Our calculator provides standard US estimations.
Does bra size change with weight loss?
Yes. Breasts are composed largely of fatty tissue. Significant weight gain or loss will directly impact both your band and cup size. Always remeasure after a weight change of 10 lbs (4.5 kg) or more.