How to Measure for an Aerie Bra Size
Two measurements, under 3 minutes. Get your exact Aerie size for Real Sunnie and band/cup styles, plus how to pick S/M/L for bralettes — no store visit needed.
Verified Jun 2026 · Source: Aerie official size chart ↗
Aerie Bra Size Calculator
Measure snugly around your ribcage (underbust) and at the fullest part of your bust.
Where to place the tape
Band sits level around your rib cage just under the bust. Bust wraps the fullest point.
- Do — keep the tape level, the same height front and back, parallel to the floor.
- Don't — let the tape ride up your back. It inflates your band and shrinks your cup.
Band & cup, from your measurements
Your underbust sets the band. The difference between your bust and underbust sets the cup — each inch of difference is one cup up.
| Bust − band | US | UK | EU |
|---|---|---|---|
| 0″ | AA | AA | AA |
| 1″ | A | A | A |
| 2″ | B | B | B |
| 3″ | C | C | C |
| 4″ | D | D | D |
| 5″ | DD | DD | E |
| 6″ | DDD | E | F |
US cup sizing is based on the inch difference; cm values are conversions. EU cup letters diverge above a D.
Picking the Right Aerie Bra in Your Size
| Style | Sizing | Note |
|---|---|---|
| Real Sunnie | Band + cup | Lightly lined, natural fit — go by your measured size |
| SMOOTHEZ | Band + cup | Smoothing / wireless — true to size |
| Bralette / wireless | S / M / L | Stretchy — choose by snug vs. relaxed preference |
Do Aerie Bras Run True to Size?
Aerie doesn't publish a built-in sizing skew — they point you to your band-and-bust measurement, their Best Fit Finder, or a free in-store fitting rather than telling everyone to size up or down. So the size you calculate above is the right starting point. A couple of things to know: bands tend to be stretchy, and bralettes and many wireless styles use S/M/L instead of band/cup, so cup fit can vary by style. If your measured size feels off in a given style, adjust with a sister size rather than re-measuring.
How a Aerie bra should fit
Once you've got your size, check it against these signs of a good fit.
- 1. Band level & parallel to floor. It should sit snug and horizontal, doing most of the support work.
- 2. Center gore lies flat. The piece between the cups should tack against your sternum, not float.
- 3. Straps rest flat. No digging and no sliding — you should fit two fingers underneath.
- 4. Cups contain smoothly. No spillage over the top and no gaping or wrinkling.
Still off? See how a bra should fit for the full checklist.
What If Your Size Doesn't Fit?
Bra fit is rarely about a single number — if your measured size feels off, you probably need a sister size, not a different measurement. Sister sizes share cup volume but shift the band. Band too tight? Go up a band and down a cup (34C → 36B). Cup overflowing? Go down a band and up a cup (34C → 32D). Both fit the same amount of tissue.
How to Measure for an Aerie Bra: Step by Step
Wear a non-padded bra
Put on a regular T-shirt bra or unlined bralette — not a push-up, sports bra, or minimizer. Padded styles add volume and skew your bust measurement.
Tip: If you can see the shape of your natural bust in the mirror, you're ready to measure.
Measure your band (underbust)
Wrap a soft tape measure snugly around your rib cage directly under your bust. Keep the tape level and parallel to the floor all the way around. Round to the nearest whole inch.
Tip: The tape should feel firm but not tight — you should be able to breathe normally.
Measure your bust
Wrap the tape around the fullest part of your bust. Keep it level but relaxed — not pulled tight, not loose. Round to the nearest whole inch.
Tip: Look in a mirror from the side to confirm the tape isn't dipping or riding up.
Calculate your cup size
Subtract your band measurement from your bust measurement. Each inch of difference is one cup size: 1 inch = A, 2 = B, 3 = C, 4 = D, 5 = DD. Aerie uses standard US cup notation.
Tip: Example: 37-inch bust minus 34-inch band = 3 inches = C cup.
Combine to get your Aerie size
Your Aerie size is your band number plus your cup letter — a 34-inch band with a 3-inch difference is a 34C. Use that for Real Sunnie and other band/cup styles. For bralettes and wireless styles, switch to S/M/L: enter your band and cup in the calculator above and check it against the size chart.
Tip: The calculator shows your Aerie size in US, UK, EU, and AU systems, with sister sizes.
Verify with sister sizes if the fit feels off
If your calculated size doesn't feel right, try a sister size: go down one band and up one cup (34C → 32D) for a tighter band, or up one band and down one cup (34C → 36B) for more room. The cup volume stays the same.
Tip: Both directions hold the same amount of breast tissue — only the band fit changes.
Next steps
Got your size? Compare it against Aerie's full chart, or check the fit checklist to make sure your bra is working as hard as you are.
Also see: how a well-fitting bra should feel · signs you're wearing the wrong bra size · bra fit troubleshooter
Measuring for another brand?
The band-and-bust method is the same across brands — only the size range and style notes differ. Brand-specific measuring guides:
How to Measure for a Victoria's Secret Bra
Band, bust, cup math · 30A–40DDD
How to Measure for a Calvin Klein Bra
Band, bust, cup math · 30A–38DD + S/M/L
How to Measure for a Savage X Fenty Bra
Band, bust, cup math · 30A–46DDD
How to Measure for a Wacoal Bra
Band, bust, cup · full-figure to K cup
How to Measure for a Knix Bra
Standard sizing + Knix's alpha-plus styles