Is 38AA Your True Bra Size?
38AA pairs a 38 band with a AA cup. Start here if your underbust lands near 38 and your bust-minus-band is about 1 inches—then confirm with a scoop-and-swoop try-on, not clothing size. AA cups are less common on mall walls than A/B; many brands fold AA into A. If 38AA is not stocked, try 38A with a shallow cup shape before abandoning the band.
Quick answer
38AA is a US/UK size: band 38 (EU often ~85) with cup AA (often near EU AA). Sister sizes 36A keep similar volume when the band feels wrong.
| US / UK | EU (approx.) | Cup difference (chart) | Sister sizes |
|---|---|---|---|
| 38AA | 85AA | About 1" (≈3 cm) | 36A |
If this size feels wrong, try this next
Start from what you feel in the bra—not from a clothing size. Change one thing at a time: usually cup volume first if the band already stays level.
Band rides up on the tightest hook
Try next: Stay near 38; add cup volume or try sister 36A
Overflow can push a correct band out of place; a bigger band often hides the real issue.
Band digs in on the loosest hook
Try next: 40 with a smaller cup
Sister sizing keeps volume while giving the ribs more ease.
Cups wrinkle but band feels good
Try next: Shallower cup shape in 38AA, or 38A if AA is empty
Empty fabric is volume or shape mismatch, not a reason to size up the band.
Quad-boob or side spill after scooping
Try next: Larger cup on 38, or a deeper-cup style in 38AA
Spill is often cup volume or shape, not automatically a bigger band.
Measure for 38AA
Soft tape, afternoon timing, skin-to-tape under the bust. Full illustrated steps: how to measure bra size.
- 1
Snug underbust
Wrap a soft tape under the bust, level around the back. Round toward even band 38 when your raw number sits near that range.
- 2
Bust at the fullest point
Lean slightly forward and measure the fullest bust without compressing tissue. Keep the tape parallel to the floor.
- 3
Check ~1" difference
Subtract underbust from bust. Near 1 inches suggests AA on a 38 band. Half-inch gaps may still wear as 38AA depending on brand.
- 4
Confirm in a bra
Try 38AA and one sister size. Scoop all tissue into the cups, fasten on the loosest hook, and check that the band stays level when you raise your arms.
38AA fit checks
- Band stays horizontal across your back when you lift arms.
- Two fingers fit under the front band—snug, not strangling.
- Center gore touches the sternum on underwire styles.
- No tissue trapped under the wire after scooping.
- Straps do not leave deep red grooves by midday.
Before judging cups, scoop tissue fully into the cups (scoop & swoop).
Nearby sizes worth comparing
Same letter on a different band is not the same volume. Use these when you are between sizes or a style skips your label.
38A
One cup up
When 38AA is close but cup volume feels off.
36A
Sister size
When the 38 band digs or floats but cup volume feels right.
36AA
Same letter, firmer band
When 38 never stays level.
40AA
Same letter, easier band
When 38 digs despite correct cups.
Sister sizes for 38AA
Similar cup volume, different band tension. Full rule and chart: bra sister sizes.
- 36A
Same size, different shape
The label is volume on a band—not a body type. If the number seems right but the bra still fights you, cup shape is often the missing piece.
Tall molded 38AA cups may gape at the top—try a shorter or stretch cup before dropping a letter.
Shallow t-shirt cups can flatten you even when the letter is right. Seamed cups usually feel truer.
A natural center gap is normal. Side-support panels help without forcing the gore.
Scoop fully first. Empty space at the top often means cup shape, not a smaller letter.
What 38AA is describing
The 38 is the band that should sit snug and level under the bust. The AA is cup volume on that band—classically about a 1-inch (roughly 2 cm) difference between bust and underbust, though brand grading varies.
EU tags often list something near 85AA. Keep both band and cup when you convert; dropping the letter is a common ordering mistake.
Two people in 38AA can look different in clothing because shape and projection change how the same inches fill a cup.
If you were sold a looser band for "comfort," you may actually belong in 38AA once cups match after a real measurement.
Wire width and cup depth matter as much as the label—shallow molded cups and stretch lace can feel like different sizes.
Cycle swelling can nudge 38AA toward a sister size for a few days; stretch cups help more than jumping multiple letters.
Who often lands on 38AA
Measured underbust near the 38-inch range with a bust difference around 1 inches is the textbook start. Athletes and postpartum bodies may shift in or out of this size within months.
Former wearers of 40 with a smaller cup letter often move to 38AA when the larger band rides up.
Store charts that skip your cup on a sparse wall push people into the wrong band—measure first, then shop the letter.
Fit details for 38AA
- Fasten 38AA on the loosest hook when new so you can tighten as elastic relaxes.
- Raise your arms—if the band rides up, fix cup volume or sister size before loosening straps.
- Straps only fine-tune lift; they should not carry the whole bust.
- Log brands where 38AA runs shallow or deep—letters are not universal.
- Hand-wash or use a lingerie bag; heat drying kills band recovery.
- Keep a sister size (36A) in rotation for high-swelling days.
38AA mistakes
Skip this: Jumping to 40 because 38 feels firm for thirty seconds.
Try this instead: Wear 38AA for ten minutes after scooping; a correct band feels secure before it feels familiar.
Skip this: Sizing up the band whenever cups overflow.
Try this instead: Stay on 38 and increase the cup letter, or change cup shape.
Skip this: Letting straps do all the lifting on a loose band.
Try this instead: A firm 38 band reduces shoulder pain and keeps wires in your fold.
When 38AA is close but not quite right
Band digs all day? Try sister 40 so volume stays similar.
Band fine but spill at the neckline? Stay on 38 and move up a cup letter.
Between two bands on tape? Try 38AA and a sister with matching volume, then pick whichever band stays level through a normal day.
Buying bras in 38AA
Mall walls under-stock some 38AA combinations; specialty and EU brands often cut deeper cups on the same letter.
Read return policies before ordering three sister sizes online.
When converting to EU 85AA, match both band and cup on the brand chart—not letter alone.
How we approach bra sizing
SizeFit tools use bust-to-underbust difference for cup signals, aligned with European clothing size standard EN 13402. Measurement vocabulary follows ISO 8559 work under ISO/TC 133.
Band and cup differences follow classic inch steps used with our calculator—then confirm with a real wear test.
Brands still cut different shapes under the same stamp. Measure, use sister sizes when needed, and keep the bra that stays level through a normal day. Fit guidance—not medical advice.
Frequently asked questions
38AA means a 38 underbust band with a AA cup—about a 1-inch bust difference on classic US charts. Shape and brand still change how it feels.
Common sisters are 36A. They keep similar cup volume while moving the band tighter or looser.
Often near 85AA, but cup letters shift by market. Check the brand chart when you shop internationally.
Letters are not standardized across brands. If cups wrinkle or spill in one brand, try shape changes or a sister size before assuming the whole size is wrong.
Measure snug underbust near 38 and bust difference near 1 inches, then try 38AA with a scoop-and-swoop. If the band rides up or digs, test a sister size before abandoning the letter.
Related guides
Support Starts With a True 38 Band
Wider bands get judged unfairly. A well-fitted 38 should feel quietly supportive under tees—not like a costume size. When it fails, people often change the letter when the band tension was the real issue.
Sister Sizes Keep Cup Volume, Change the Band
When cups already sit well but the band digs or rides up, sister sizes let you change tension without throwing away the volume that worked. They are a fitting tool—not a reason to skip measuring.
Is 36A Your True Bra Size?
36A pairs a 36 band with a A cup. Start here if your underbust lands near 36 and your bust-minus-band is about 1 inches—then confirm with a scoop-and-swoop try-on, not clothing size.