I think German has borrowed the word "egal" from French "égal". "Egal" is related to the English word "equal" (=the same), so the sentence literally means "This is (all) the same to me", i.e. "I do not care/mind".

Generally, "egal" is only used in the sense of "I don't care". In sentences like "All men are equal", you wouldn't use "egal" in German but a different word: "Alle Menschen sind gleich".

@Katherle: The first part of your answer is correct, ie. "das ist mir egal" is "that is all the same to me"; but the word "egal" is also used in another context as in the sentence "das ist egal" with the (neutral) meaning "it makes no difference" as for example in a sentence like "Soll ich um 3 oder um 4 kommen?/Should I come at three or at four o´clock? possible answer "das ist egal, die Party geht den ganzen Nachmittag"/"That makes no difference=you can come at any time you like, we will party all afternoon..." Noch viel Spaß!

Thank you very much

the literal translation is 'It is to me the same'. It means, I don't care or it doesn't matter to me.

'das ist mir egal' translates to " it is equal to me", 'same difference', 'it's all the same to me.' where 'Alle Menschen sind Gleich' translates to "all men are similar" = "all men are the same"

…

equal =/= similar

For German Czech speakers: “das ist mir egal” → “to je jedno” or “to je mi jedno”?

Or in other words, is “das ist mir egal” more intensive, with a hint of “…and I don't care” compared to “das ist egal”?