What was Marilyn Monroe's dress size?

Question

This question has gotten thrown around a lot, and the only reason I think it's appropriate here is because her dress size and status as a sex symbol are used in arguments about body image, BMI, and health. However, the prevalent "common knowledge" is that she was anywhere from a size 12 to a size 16 for most of her career, which is rather large by today's standards.

http://marilynmonroepages.com/facts.html , under General Facts making the claim for size 12.

http://jezebel.com/5299793/for-the-last-time-what-size-was-marilyn-monroe , talking about the claims.

So my question is, by modern measuring standards, what dress size was Marilyn Monroe at the height of her career? (Let's say 1953, when Gentlemen Prefer Blondes was released)

Answer 1

This is another one of the those terrific questions, where most of the research is already done in the question

The claim I am addressing is: Was Marilyn Monroe was much larger a modern size 12, the same as a modern size 12, or smaller than a modern size 12?

Larger?

Some people claim she was large, including Roseanne Bar:

"I'm more sexy than Pamela Lee or whoever else they've got out [in Hollywood] these days. Marilyn Monroe was a Size 16. That says it all."

[Source: The Phoenix Gazette. "Say What?" 23 February 1996, via Snopes]

Barr is not a reliable authority and I haven't found any real evidence of this.

Same size?

The link you gave claims she was a size 12.

However, dress sizes are poorly standardized and have changed over time (Ref). A size 12 in the 1940-50s has become a size 6 now (Ref). So this information isn't very helpful.

Smaller

But, in fact we have evidence that she was smaller than a modern size 12.

US catalog sizes put modern day Size 12 as roughly:

Est. weight 155lb (70kg) Bust 38.5" Waist 29.5" Hip 40"

Your own source, quoting from a biography, has two sources for Monroe's measurements:

(studio's claim): 37-23-36 (inches)

(dressmaker's claim): 35-22-35 (inches)

Both of those are considerably smaller than a modern size 12. Those dimensions don't particular fit any of the US catalog sizes (and I am sure many women would attest that is also their experience.)

It also puts her weight at:

118 pounds 53.5 kilograms

which is under the Size 12 estimate. (I acknowledge that stating someone's general weight to within half-a-kilo is a overly precise.)

Furthermore, we have experimental evidence:

Here is a quote from a fashion writer, Sarah Buys

Contrary to received wisdom, she was not a voluptuous size 16 — quite the opposite. While she was undeniably voluptuous — in possession of an ample bosom and a bottom that would look at home gyrating in a J-Lo video — for most of the early part of her career, she was a size 8 and even in her plumper stages, was no more than a 10. I can tell you this from experience because a few weeks ago, I tried to try on her clothes.

Source: "Was Marilyn Monroe a Size 16?" The [London] Times, 11 April 2009, via Snopes

Conclusion

Marilyn Monroe was smaller than a modern size 12.

Asking what size she actually was makes too many assumptions to answer: i.e. that dress sizes are well-standardized, human dimensions can be fit into a single scale, and they are stable.