how much time needed to check in for US flight at CDG?

Ask the airline (or their website, or your travel agent if you bought the ticket through one). It should also say on your confirmation.
It is the airline that dictates this.

I've always tried to check in about 3 hrs before any international flight, either going or coming back. Large airports anywhere can be a 'zoo' and I'd rather be safe than sorry.

Ditto what Nancy said. I aim to never find myself running through an airport in a mad dash so I go early. I go 3 hours early to CDG and if I'm at my gate early I have a cup of coffee and read my book.

I always do three hours for a US flight out of CDG.

Ditto -- 3 hrs for a CDG departure to the US. Last October it took me 90 minutes to clear check in and get up to the gate.

If you plan to get your VAT refund at CDG budget time for that as well.

We always check-in at least 3 hours for an international flight. At CDG remember that not only is there security, but also passport control to clear.

Standard recommendation is three hours. Sometimes that is excess and sometimes barely enough. There are a lot of factors that you cannot control and as is often stated, " I would rather be an hour early than ten minutes late." For CDG (not one of my favorite airport) I might push it to four hours. Curious, why did you post this question under Technology Tips?

Easycdg.com says 3 hours. Are you flying in business class or first class? If so, you can cut that time down to 2 hours and be pretty safe because of the separate (i.e. shorter) check in/luggage drop line for business class passengers.

My daughter took 4 hours from boarding the train at Gare de Lyon until boarding the plane last week. They were already boarding the plane when she arrived at the gate, so depending on circumstances, 4 hours might be cutting it close!

Keep in mind that you may undergo another thorough security check at the boarding lounge, particularly if you are flying with a US operator. Many airlines want you in the plane, not just the lounge, a half hour before departure from the gate and may close the cabin door earlier than the stated "departure" time.

CDG, I am so sorry. Last flight out of...well...anywhere else must have been full, ay?

3+ hours. My last experience there was not...well, good.

Bon voyage!

cabalist....that's discouraging. What in particular were the bad points for you?

There was a strike going on.

The lines seemed to be super long and not quite as controlled as I have seen in other large cities. It gave the distinct impression that no one knew what was going on.

The check-in clerk was sick--really sick. Coughing and sputtering over his hands and everything that he was dealing with. I imagine it had something to do with the strike (ie he was brought in when he really should have been at home...or the hospital).

We had to pay for overage on our luggage, which is standard for us. We had already done so but, for some reason, had to go to another location (within site of our check-in line), and get a printed receipt. This was bad enough...

But then we had to take the receipt back to the sick clerk who, by now, had other customers (an hour long line at least) to deal with. AND HE COULD NOT FIGURE OUT HOW TO LOAD THE PAPER IN HIS LITTLE PRINTER. So it took him ANOTHER HOUR to take our receipt and give us the tickets THAT HE HAD ALREADY PRINTED BEFORE WE LEFT TO GET THE RECEIPTS. YES, all he had to do was literally hand us our tickets and take our receipt, no computer work at all (he said so when it finally happened). Sorry for the ALL CAPS. It was an exasperating experience when you know that it can be (and is) done so much better in other cities/countries.

CDG does not seem to know what is going on. This was my last experience (worst of three). Sorry. Love France, food, and culture. Airport? Not so much.

cabalist... I suppose a strike could trigger a similar episode elsewhere but that really was horrible. There was nothing you could have done to improve it either.

My husband forgot that he had a liquid in his carryon bag. TSA took their sweet time going through his bag, smaller backpack looking for STUFF and swabbing for drugs! It then took my husband ten minutes to repack and get his belt and shoes on. When I said their sweet time, I mean it took a good 25 minutes for a tiny carryon bag and backpack. The TSA agent did not care one bit. He actually stood chit chatting with another agent for five minutes before he even started with my husband.
Give yourself a lot of time!