Calculate My Bra Size & Find the Perfect Fit

The most accurate Bra Size Calculator on the web. Stop guessing your measurements and start feeling comfortable today.

Bra Size Calculator

IN CM

Region

Fit Preference

How to Measure Bra Size: A Step-by-Step Guide

how to measure underbust for bra band size

Step 1: Measure Your Band Size

To find your accurate band size, wrap a soft measuring tape around your ribcage, directly under your bust. Make sure the tape is level and snug, but not too tight—you should be able to breathe comfortably. Exhale deeply and round to the nearest whole number to get your underbust measurement.

measuring bust size at fullest part for cup size

Step 2: Measure Your Bust Size

For your bust measurement, wrap the tape loosely around the fullest part of your chest (usually across the nipples). Keep the tape parallel to the ground to ensure accuracy. Avoid pulling the tape tight; it should rest gently against your skin. This number helps determine your cup size.

Bra Size Charts & Guides

International conversion and sister sizing tables.

International Conversion

US / CA	UK	EU (Europe)	FR (France)	AU (Australia)
32 A	32 A	70 A	85 A	10 A
34 B	34 B	75 B	90 B	12 B
36 C	36 C	80 C	95 C	14 C
38 D	38 D	85 D	100 D	16 D
40 DD	40 DD	90 E	105 E	18 DD
42 DDD	42 E	95 F	110 F	20 E

Band Size Guide

Underbust Measurement	Band Size
26 – 27 inches	30
28 – 29 inches	32
30 – 31 inches	34
32 – 33 inches	36
34 – 35 inches	38
36 – 37 inches	40

Cup Size (Difference)

Difference (Bust – Band)	Cup Size
1 inch	A
2 inches	B
3 inches	C
4 inches	D
5 inches	DD / E
6 inches	DDD / F

Sister Size Chart

If your bra doesn’t fit, try a “Sister Size” (same cup volume, different band).

If you wear…	Sister Down (Tighter Band)	Sister Up (Looser Band)
32 B	30 C	34 A
34 C	32 D	36 B
36 D	34 DD	38 C
38 DD	36 DDD (E)	40 D
40 DDD	38 G	42 DD

How to Know It Fits Perfectly? The 3-Step Check

The Band Should Be Snug & Level

The band provides 80% of your support. It should sit parallel to the floor across your back without riding up. You should be able to slide only two fingers under the band. If it rides up your back, your band size is likely too big.

No Gaping or Spillage

Your breasts should fully fill the cups with no gaping edges or wrinkling fabric. Conversely, there should be no spillage over the top or sides (often called the “quad-boob” effect). The wire should sit flat against your ribs, encircling the breast tissue completely.

Center Gore Lies Flat

The center piece (gore) between the cups must lie flat against your sternum. If it floats away from your chest, the cup size is too small. Straps should sit comfortably on your shoulders without digging in or slipping off.

FAQ

How do I accurately calculate my bra size at home?

To find your perfect fit using our bra size calculator, you need two measurements: your band size (underbust) and your bust size (at the fullest part). While traditional charts can be confusing, the mybrasize.net tool simplifies this. Simply wrap a measuring tape snugly around your ribcage for the band, and loosely around the fullest part of your chest for the bust. Enter these numbers into our calculator, and it will instantly compute your exact size, filtering out the complex math often required for different brand standards.

How does the AI Bra Size Calculator differ from a standard size chart?

Standard size charts rely on static, generic averages that often lead to poor fits. Our AI-powered bra size calculator uses advanced algorithms to analyze your inputs against thousands of data points regarding fabric stretch, brand variations, and body shapes. This AI solution offers a more personalized recommendation than a simple chart, ensuring that the result you get for my bra size accounts for nuanced differences in sizing systems (like US, UK, and EU standards).

Why does my bra size result seem different from what I usually wear?

It is a common myth that your bra size remains static. Factors such as weight fluctuations, hormonal changes, and age can alter your measurements. Additionally, many women unknowingly wear the wrong size (often a band too loose and a cup too small). If our bra size calculator suggests a different size, trust the measurements. A proper fit should have the center gore lying flat against your sternum and the band sitting parallel to the ground without riding up the back.

What are “Sister Sizes” and how do they help find my bra size?

“Sister sizes” are a group of bra sizes that share the exact same cup volume but have different band lengths. For example, if a 34C fits your cups perfectly but the band is too tight, your sister size is a 36B. Our AI-enhanced tool doesn’t just give you one number; it helps identify your sister sizes. This is crucial when shopping for brands that may run tighter or looser than average, ensuring you always find a comfortable fit regardless of the label.