It's more than enough if you are planning on living like the average local Chinese person, but it's nowhere near enough if you plan on living like the average American while in China.

I'm not talking about the food, although it is obviously more expensive to eat imported foreign food, I'm talking about your expectation for housing, comfort, hobbies and lifestyle in general.

If you plan on having a detached house with a yard in a tier-2 city in China it's going to be several times more expensive than in a similar US city, but if you are okay with living in a low rise residential building with no elevator then you can save a ton of money.

If you want thermostat heating and cooling in your home here again you are going to pay through the nose, but if you are okay with your regular wall mounted air conditioner it's fine, even better if you can go with no air conditioner at all.

If you want a fully equipped kitchen with a built in oven, dishwasher and such it's going to cost you an arm (not sure I have even ever seen a dishwasher in China LOL), but if you can do with two electric cooking plates and a microwave then good on you.

As far as housing and comfort go, it's things like that that will determine what budget you need in China, if you want the American / first world comfort it's actually more expensive in China than in America, but if you can go with the Chinese idea of comfort then you can save a ton of money.

Going out in China is generally really cheap especially if you are well located and everything is within walking distance of your home, but it can get pricey here again if you want to partake in activities beyond just hanging out at the park or at the mall, like karting for example to take something I know, it's a pretty expensive thing to do in China compared to America since it's far less common and the people who partake in it are generally well off.

Food is cheap, dirt cheap even, but the quality is questionable, if you want proper food that doesn't have a chance to give you the runs it can get as expensive as in the US or even more, and I'm not just talking about imported stuff but quality locally produced food that cater to the delicate stomachs of foreigners, and your friend if he grew up in America is also a foreigner who will probably have some stomach problems with the food in China, different bacteria, different to non-existent hygiene standards, etc...

1400 is fine if you can live like a Chinese, it's really stretching it if you plan on having some first world comfort and activities.