The size of a bra is based on two distinct measurements: the underbust (below the breast) and the bust (at the fullest point). The difference between these two values determines the cup letter, while the underbust measurement sets the number (80, 85, 90, etc.). Without these two data points, any attempt at selection remains approximate.
Underbust and bust: two measurements, two functions
The underbust is measured horizontally, just below the breast, with a tape measure flat against the skin. This number corresponds to the band of the bra, which provides the majority of support. A tape measure that is too loose skews this measurement upwards and leads to a band that is too wide, which rides up in the back.
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The bust is measured horizontally at the fullest part of the breast. To avoid compressing the breast tissue, the tape should be snug but not tight. A reliable tip: wear a thin, unpadded bra while measuring, which does not distort the natural volume.
The difference between these two measurements gives the depth of the cup. At Etam, every additional centimeter of difference raises the cup letter: A, B, C, D, E, and beyond. Consulting the Etam bra size guide allows you to cross-reference these two values and obtain the corresponding size in the French system directly.
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Correspondence between Etam cups and international sizes
One point that most size guides overlook: a size 90C in France does not correspond to a 34C in the US in the same way across brands. Etam has published correspondence charts by geographic area (FR, ES, IT, DE, UK, US) since the redesign of its American site in 2023-2024. The discrepancies mainly concern the cup letter and the band number.
The French system uses centimeters (80, 85, 90), while the Anglo-Saxon system uses inches (32, 34, 36). The direct conversion is not always linear. A woman who wears 85B in France may find herself between two sizes on a UK or US grid.
Before ordering from the international Etam site or comparing with another brand, checking the specific correspondence chart helps avoid returns. Etam displays these equivalences directly on its product pages for the American market.
Sister sizes: adjust without changing everything
The concept of sister size addresses a common issue: the right cup letter with a band that is slightly too tight or too loose. The principle is simple. Going up a band size requires going down a cup letter to maintain the same volume. Conversely, going down a band size requires going up a cup letter.
For example, if an 85C is tight at the band but the cup fits, the sister size to try is 90B. The overall volume of the cup remains nearly the same, but the band becomes more comfortable.
This mechanism is particularly useful in three situations:
- A specific model runs small in the band (common in rigid lace models)
- A weight gain or loss alters the underbust measurement without significantly changing breast volume
- A purchase between two collections with slightly different cuts
Trying on the sister size in-store takes a few minutes and prevents settling for an ill-fitting size by default.
Etam bra shapes and their impact on size choice
Size alone is not enough. At Etam, the “Numéros” range illustrates how the shape of the cup alters the fit and comfort at the same size. A plunging push-up (N°2) brings the breasts together and lifts them, which can create a feeling of a cup that is too small if the model compresses the sides. A wireless triangle (N°8) offers under-bust support without rigid structure, suitable for lighter cups but insufficient for fuller breasts.
Some concrete references on Etam shapes:
- Thin cups (N°4, N°5, N°6) provide a natural shape and suit most body types without altering perceived volume
- The balconette (N°9) exposes the upper bust with a plunging neckline but requires a well-filled cup to avoid gaping
- Scarf models (N°3, N°7) offer a V-neckline that visually elongates the bust, with more pronounced side support
Since 2023-2024, Etam has expanded the Numéros range to include deeper cups than its classic collections. Women with fuller breasts can find accommodating models (balconies, thin cups) that were not previously available in this line.
Concrete signs of a poorly fitting size
Wearing the wrong size is not limited to vague discomfort. Several physical indicators can help identify the problem precisely.
The band rides up in the back: it is too large. The band should remain parallel to the ground, at the same height in the front and back. If it forms an upward arc, go down a band size (and up a cup size to compensate).
The underwires press into the breast tissue instead of lying flat against the ribcage: the cup is too small. The underwire should frame the breast without compressing or cutting into the sides.
The straps constantly slip despite being tightly adjusted: the band is likely too wide. The main support comes from the band, not the straps. Tightening the straps never compensates for an ill-fitting band.
The cup fabric gapes or forms wrinkles: the cup is too large, or the shape does not suit the body type. Trying a model with thinner cups or a smaller sister size often resolves this issue.
A properly fitting bra closes on the loosest hook when purchased. Tighter hooks are used to compensate for the elastic loosening over time. Buying a model that only closes on the last hook guarantees a very short lifespan.