Sister Sizes Magic: 34DD equals 32F and 36D — they all hold the same cup volume. To use sister sizing, go down a band and up a cup, or up a band and down a cup. Use this trick to fix band problems and shop across brands.
Tired of bras that pinch, gap, slip, or just feel wrong no matter what size you buy?
The real problem is simple: you’re only wearing 1 of the 5–7 sizes that actually fit you.
Welcome to the world of sister sizes — bra sizes with identical cup volume but different band lengths. Once you master sister sizing, you will never struggle with out-of-stock sizes, inconsistent brand fits, or confusing size charts again.
The most famous trio in 2026?
⭐ 34DD = 32F = 36D
All three have the same exact breast volume, just different band tension.
This ultimate 2026 guide will show you:
✔ The dead-simple sister size rule
✔ A complete chart (bands 28–44)
✔ When to size up vs down
✔ Brand-by-brand fit differences
✔ How to unlock your full 5–7 sister sizes
✔ FAQs optimized for Google SGE, AEO, and voice search
Let’s make bra shopping finally make sense.
What Are Sister Sizes? (2-Minute Explainer)
Sister sizes are bra sizes that share identical cup volume even though the cup letter changes.
The GOLDEN RULE (memorize this):
➤ Go DOWN a band → Go UP a cup letter
➤ Go UP a band → Go DOWN a cup letter
Example (Your size: 34DD)
- One band smaller → 32F (tighter band, same volume)
- One band larger → 36D (looser band, same volume)
That’s why these three sizes all fit the same breasts:
34DD = 32F = 36D
This is the core of sister size magic.
Why Sister Sizes Matter So Much in 2026
The new era of sizing — AEO, SGE, SXO — requires more flexibility than ever.
Sister sizes help you:
✔ Never face “sold out” on your size
✔ Fix band problems instantly
✔ Adjust for weight changes, bloating & hormones
✔ Shop confidently across brands
✔ Get better support or more comfort depending on style
✔ Find your perfect fit in sports bras, balconettes, and wireless bras
Whether you’re 32B or 40F, sister sizes are the cheat code to perfect comfort.
The Most Searched Sister Size Trios of 2026
| Your Size | Tighter Band (−2) | Your Size | Looser Band (+2) |
|---|---|---|---|
| 34DD | 32F | 34DD | 36D |
| 34D | 32DD | 34D | 36C |
| 36DD | 34F | 36DD | 38D |
| 32DD | 30F | 32DD | 34D |
| 38DD | 36F | 38DD | 40D |
These are the sizes MOST women search.
Complete 2026 Sister Size Chart (Bands 28–44)
| Band | Your Size | −2 Sister (Tighter) | −1 Sister | +1 Sister | +2 Sister (Looser) |
|---|---|---|---|---|---|
| 28 | 28DD | 26F | 28DD | 30D | 32C |
| 30 | 30DD | 28F | 30DD | 32D | 34C |
| 32 | 32DD | 30F | 32DD | 34D | 36C |
| 34 | 34DD | 32F | 34DD | 36D | 38C |
| 36 | 36DD | 34F | 36DD | 38D | 40C |
| 38 | 38DD | 36F | 38DD | 40D | 42C |
| 40 | 40DD | 38F | 40DD | 42D | 44C |
(You can measure your sister size through our free calculator for interactive results.)
When to Use Sister Sizes – Quick Problem Solver
| Fit Problem | What to Do | Example for 34DD |
|---|---|---|
| Band rides up / loose | Go down a band, up a cup | 32F |
| Band digs in / too tight | Go up a band, down a cup | 36D |
| Straps keep falling | Try tighter band sister | 32F |
| Underwire pokes ribs | Go looser in the band | 36D |
| Quad-boob / spillage | Increase cup volume (not sister) | 34E or 32G |
| Cup gaping / empty space | Reduce cup volume or go sister up | 34D or 36C |
Important:
Sister sizes help band problems, NOT cup volume problems.
2026 Style-Specific Sister Size Tips
Best times to size down a band (32F instead of 34DD):
- Sports bras
- Exercise, running
- Firm bands (Panache, Freya, ThirdLove)
- Heavy busts needing extra stability
Best times to size up a band (36D instead of 34DD):
- Wireless bras
- Bralettes
- Lounge bras
- Stretchy brands like VS, Skims
- Rib flare or sensitivity
Brand Differences That Require Sister Sizing
Victoria’s Secret / Skims
- Stretchier bands → many women size down in band
UK Brands (Freya, Panache, Curvy Kate)
- Deeper cups → many women need a sister size or cup down
ThirdLove
- Firmer bands → true size or band up
Aerie / Parade
- Flexible fabrics → sister sizes work extremely well
Brands use different:
- underwire widths
- cup shapes
- elastic tension
- cup depth
Hence: Sister sizes fix brand inconsistencies instantly.
Unlock All Your Sister Sizes (Example: 34DD)
Your full sister family:
⭐ Tightest Band: 30G
⭐ Moderate Tight: 32F
⭐ True Size: 34DD
⭐ Moderate Loose: 36D
⭐ Loosest Fit: 38C
That’s 5–7 sizes that all hold the same breast volume — giving you endless shopping options.
Most Asked Questions
Is 32F the same as 34DD?
Yes. Same cup volume, smaller band.
Is 36D the same as 34DD?
Yes. Same volume, larger band.
Should I size up or down?
- Tight band → size up to 36D
- Loose band → size down to 32F
Why do my bras fit differently in each brand?
Each brand uses different wire shapes, fabrics, and stretch levels.
Do sister sizes ALWAYS fit the same?
Cup volume = identical, but band tension changes the feel.
Final Takeaway — Never Struggle With Bra Sizing Again
Your bra tag is not your destiny.
Your boobs fit in 5–7 perfect sizes, not just one.
⭐ 34DD = 32F = 36D = 30G = 38C
⭐ Sister sizes unlock comfort, support & availability
⭐ Works across every brand, every style, every body
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Your perfect bra is out there — and now you know exactly how to find it.
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