FR to US conversion

FR 100F in US Bra Size

Convert 100F from French sizing to US sizing, with the full international table, sister sizes, and practical fit checks in one place.

Instant answer

100F (FR) =

38DDD US

In this sizing table, 100F in French sizing converts to 38DDD in US sizing.

Full conversion table for 100F (US 38DDD)

38DDD bra size conversion across US, UK, EU, French, and Australian sizing.
US	UK	EU	FR	AU
38DDD	38E	85F	100F	16E

Bra sizing varies between brands. Use this as an accurate starting point and check the fit.

What this conversion means

This reverse conversion starts with the label you already have: 100F (FR). The matching US record is 38DDD, and the table shows the same size across UK, EU, French, and Australian systems for easier retailer comparison.

Sister sizes for the US equivalent (38DDD)

Sister sizes: 40DD can be worth checking when the cup volume feels close but the band needs a different feel.

What measurements make a 100F?

The useful way to read 100F is to separate the band from the cup step. In the current calculator formula, the closest starting range is about 37-39 inches (94-99 cm) under the bust and about 43.5-44.5 inches (110-113 cm) around the fullest part of the bust. The band comes from the underbust rounding, while the cup step comes from the difference between bust and band. This page uses 38DDD as the US equivalent for those measurement notes.

Is 100F big or small?

Whether 100F feels small, average, or full depends on the body and on the brand. In this size set, the US equivalent uses a fuller band and a fuller cup step. Cup letters are relative to the band, so a D on one band is not the same volume as a D on every other band. The most useful question is whether the band stays level and the cups hold smoothly, not whether the label sounds large or small.

If 100F doesn't fit right

Band rides up: The band may be too loose or stretched out; try a snugger band or compare the snugger sister size.

Cups gape: The cup may be too roomy, too deep, or pulled away by a loose band; check the band before changing cup volume.

Cups spill: The cup volume may be too small or the cup shape may be too closed; try one cup step up before changing the band.

Straps dig in: The straps may be compensating for a band that is not supporting enough; reset the band fit before tightening straps.

How 100F differs between brands

100F can shift in feel from one retailer to another because brands grade bands and cups in their own way. A firmer elastic can make the same band feel smaller, and a shallow or narrow cup can make the same cup letter feel different. Check the retailer chart, read fit notes when available, and compare the label against the brand and region sizing guide before treating the conversion as final.

Shopping for 100F

100F is easiest to compare when you try shapes that show both cup volume and band tension clearly. If the cup is in a lower or middle step, lightly lined T-shirt styles can make gaps easy to spot. Fuller cup steps often benefit from styles with steadier side support, deeper cups, or a balconette shape depending on breast shape. For special outfits, compare the fit needs in the outfit guides before choosing a strapless, plunge, or backless option.

Bras in your size

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Everyday Fit Store

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Comfort Band Co.

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Soft Cup Edit

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FAQ

Is 100F the same as 38DDD in the US?

In this dataset, 100F (FR) converts to 38DDD in US sizing. Some brands publish their own charts, so use this as the closest standard label and still check the real fit.

What is 100F in European sizing?

100F (FR) matches the same base record as 85F (EU). The full table on this page shows each supported label side by side.

How do I check the fit of 38DDD?

Check that the band stays level, the cups sit smoothly without spilling or gapping, and the straps are not doing all the support work. The converted US size is a starting point, not a guarantee.

What sister sizes work with 38DDD?

40DD are the closest sister-size options for 38DDD in this dataset. Try a sister size when cup volume feels close but the band needs to feel snugger or looser.

Why do bra sizes differ between countries?

Bra labels are written differently across US, UK, EU, French, and Australian systems. Cup letters can also diverge after D, so a converted label is a starting point rather than a promise of identical fit.

What measurements usually make 100F?

100F maps to US 38DDD here. The current calculator formula points to about 37-39 inches underbust and 43.5-44.5 inches bust, or roughly 94-99 cm and 110-113 cm. Treat that as a starting range and then check the real fit.