I am size thirty eight
I am size thirty eight
My size is thirty eight
Are both of them possible?. Thank you.
7 Answers
I agree with the previous answers.
When someone says "What size are you?" You can respond with:
"I am a size thirty eight" (most common)
"My size is thirty eight" (correct but less common)
I think the first one is more common, but both are functional. I believe it is also expressed as "I am a size 38".
I suspect that we're not speaking of US dress sizes?

"my size is thirty eight"=mi talla es la 38.
"I am a size thirty eight"=tengo una talla 38
I agree with Qfreed, "I am a size thirty eight" sounds much natural and it's what I would say, although your sentences do make sense.
No, they are British sizes
British sizes for what?! I think this is a European size. It would be equivalent to a size 10 in England.
You can say:
Tengo talla 38.
I think "my size is thirty eight" is right too, but you can't say "I am size thirty eight", but you can also say I am a size thirty eight, or simply just say thirty eight.
After all the debate about what size you are (none of my business) let me say that your two suggestion are both fine and would/will be understood (so long as you are giving the information where they use that sizing). You could also use "I take a size 38", a compromise between what you and Marianne say.
Nothing to do with the question but are you actually a French speaker? Your use of "What do you think in it" sounds French to me. "By their prepositions ye shall know them" as a professor of French of my acqaintance once said.