Breast Size Comparison Visualizer:
Compare Bra Sizes Side by Side
Compare any two bra sizes by band, cup step and sister-size relationship, then open a detailed fit guide for the exact pair. Use the visual tool for a fast answer or browse the full A–Z directory when you want the deeper fit logic.
Compare Any Two Bra Sizes Instantly
Pick Size A and Size B — get band difference, cup volume, sister sizing, and a side-by-side silhouette in seconds.
See how cup letters change across band sizes and compare visual cup-size examples in the dedicated AA–K visual guide. Use it as context, not as a photo-based diagnosis — body shape and projection can make the same labeled size look very different.
Here’s what the bra industry never explains clearly: the same cup letter doesn’t mean the same size. A 34B and a 36B look identical on the label but hold different amounts of volume. A 32D and a 34C look different on paper, yet they are sister sizes with similar cup capacity and different band tension.
This directory is built to fix that confusion. Every comparison page covers the measurements, the math, the fit signs, and the exact situations where one size works better than the other. Click any comparison below to get the full breakdown.
How to Use This Directory
Don’t know your size?
Start with the Bra Size Calculator. Get your band and cup in 2 minutes. Then come back to compare.
Band feels wrong?
Use sister size logic: go up/down one band and flip the cup. Similar cup capacity, different band tension. Find the exact relationship in the comparisons.
Open a comparison
Read the quick answer first (10 seconds). Then scan the fit signs to confirm which size works on your body.
Shopping across brands?
Sizes shift by brand. After comparing, use the Brand Size Decoder to decode VS, Aerie, ThirdLove & more.
Most Popular Comparisons
The comparisons women search most — answered with volume data, fit signs, and sister size alternatives.
Breast Volume by Cup Size (34 Band)
Approximate averages. Volume increases with band size too — a 36C holds more than a 34C.
👉 Want exact numbers? Use the Breast Volume Calculator
Sister Size Chart
Each row shares the same cup volume. Move left for a tighter band, right for a looser one.
| ← Tighter Band | Center Size | Looser Band → | Relationship |
|---|---|---|---|
| 32A | 34AA | 36AAA | Sister |
| 32B | 34A | 36AA | Sister |
| 32C | 34B | 36A | Sister |
| 32D | 34C | 36B | Sister |
| 32DD | 34D | 36C | Sister |
| 32DDD | 34DD | 36D | Sister |
| 34DDD | 36DD | 38D | Sister |
| 36DDD | 38DD | 40D | Sister |
| 38DDD | 40DD | 42D | Sister |
Rule: go up one band + down one cup = same volume. Down one band + up one cup = same volume. Use the Sister Size Calculator for any size instantly.
All Bra Size Comparisons A–Z
Organized by band size. Every page covers volume difference, sister sizing, and exact fit advice.
No comparisons found
Try searching for a specific size like “34C” or “36B vs 38A”
Use the comparison tool instead →Found the Better Size? Shop by the Support You Need
Use your comparison result as a starting point, then check the brand’s own size chart and return policy. A sister size can preserve similar cup capacity, but cup shape and band stretch still vary by bra.
Everyday T-shirt Bras
Useful when you want a smooth everyday fit after confirming the better band-and-cup combination.
Browse on Amazon →Full-Coverage & Support Bras
A practical next stop if your comparison points to more cup depth, side containment or stronger band support.
Browse on Amazon →Wireless Comfort Bras
Good for comfort-focused days when you still want to shop by the size relationship you just confirmed.
Browse on Amazon →Affiliate disclosure: As an Amazon Associate, Bra-Calculator.com earns from qualifying purchases. Availability and sizing vary by brand; always verify the product’s own size chart before ordering.
Complete Fit Toolkit
These tools work together. Start with the calculator, then use comparisons to dial in your exact fit.
Bra Size Comparison FAQ
The most searched questions — answered clearly, without the jargon.
Not Sure Which Size to Compare?
Start with the Bra Size Calculator to find your true size in under 2 minutes — then use this directory to understand every adjustment from there.
Amelia reviews Bra-Calculator.com fit content with a practical focus on measurement logic, sister sizing, cup-shape differences and real-world fit symptoms. Read her bio and credentials →