The right way to say this in the UK would be "I need to go to the toilet" or just "I need the toilet".

Contrary to puppetsock, the word "WC" is hardly used these days, and younger people especially would not know what it meant. You might use it to excuse yourself from an audience with the Queen, but for everyone else you should say "toilet".

"Bathroom" would be understood, but you might get some sarcastic comments of "why, do you need a bath?"

(Excuse me,) I need to use the toilet/bathroom/restroom.

Exactly how that room is named depends on the continent. The commenters are right, toilet is most often used in British English, while Americans prefer restroom or bathroom.

The phrase is not limited to urination:

(Euphemism) to urinate or defecate. May I be excused to use the bathroom? I have to use the toilet.

(source: The Free Dictionary)

but what you're doing there exactly is nobody's business but your own.

Excuse me for a moment please

This leaves both purpose and destination unstated, but by making it clear that the absence will be very temporary, does not cause anyone to think that it is a total departure. This will usually be understood sufficiently in context.

There are of course, many euphemisms, some gender specific, some not, some considered more polite than others.

• I need the small room.


• I need to powder my nose. (a bit old-fashioned.)


• I need the lav. (out of date?)


• You don't buy beer, you rent it. (perhaps too graphic, but less so than "piss").


• I need the John.

and many many others

Devon's answer reminded me of

When Nature is calling, plain speaking is out,
When ladies, God bless 'em, are milling about,
You make water, wee-wee, or empty the glass;
You can powder your nose; "Excuse me" may pass;
Shake the dew off the lily; see a man 'bout a dog;
Or when everyone's soused, it's condensing the fog,
But be pleased to consider and remember just this -
That only in Shakespeare do characters piss!

one stanza from this which i first read in The Lure of the Limerick

There is no polite way to bring the image into others' minds of your spraying out waste water from your privy parts. The polite way to excuse yourself is to say some variation on

I need to go.

or

I'll be back in a minute.

If it's a need at that exact moment, then it's pretty obvious in almost all situations what that need is and you don't need to spell it out at all. "Urinate", being latinate, is going to come across as clinical. "Pee" is childish, "tinkle" or "wee" even more so. "Piss" and "slash" can be rudely vulgar or amusingly friendly depending on your company.

If you need to explain yourself, you can say where you're going instead of what you're doing. You can say toilet or any of the other names for the place but it's still usually gender binary: "I need to go to the Men's", "the Gents'", or "the Ladies'" works better than discussing the plumbing.

I am very surprised that none of the answers or comments so far have mentioned the word "loo", as in "I need the loo"or "Where is the loo?". It is at least as polite as toilet.

In addition, there is a certain snobbery about that word, with many users of BrE considering (quite incorrectly, on linguistic grounds) that "toilet" is a mealy-mouthed, lower-class way of saying "lavatory".

If you wish both to avoid taking a stand one way or the other on the snobbery and to avoid explicitness, you can always say something like "I must disappear for a moment", or "Excuse me for a moment".

I need to...

• ...see a man about a dog.


• ...shake the dew off the lily.


• ...condense some fog.


• ...tinkle.


• ...pee.

These are all colloquial and somewhat humorous ways people often convey this information.

In the US, it is acceptable to say "I need to freshen up" if it is not urgent. This gives the listener the ambiguity that the urinator is just washing their hands and applying make-up, on the listener's behalf.

In the UK you probably want to indicate you need the WC. That's "water closet." Depending on the exact cultural group you are dealing with it may be bathroom, washroom, toilet, restroom, or a couple other things. But nearly everybody in the UK will understand WC. Especially if you are in some kind of public place like the subway or a theater or cinema or pub or such places.

It's definitely cultural. I've learned not to try to ask for a "washroom" in the USA, but to be sure to say "bathroom" even when it's a public facility with absolutely no bathtubs.