If The USA 'Fiscal Cliff' is reached and tax increases are enacted how much will you be out of pocket?

I have read all this Fiscal Cliff stuff and honestly thought it was all speculation, but upon reading more about it I am now aware that it is an actual maximum limit of borrowing. Reports that I've read say that this will occur on Monday if an agreement is not reached to increase the upper limit of borrowing by the US government before then.
The fiscal cliff was a specific maximum amount that when reached an automatic tax increase and spending reduction come into effect. The aim of having a 'fiscal cliff' was to make those who held the purse strings pull their finger out and actually do something about spending above their means, obviously this hasn't happened.
I'm interested to know if you guys over there in the USA have been told how much tax will be withheld from your next pay if this does in fact occur? From what i have read the next pay after the cliff is reached will have an automatic deduction of the increased tax. I can only imagine that this will cause huge strain for most of the population. So, do you know how much will be withheld? Like if you were expecting $300 for your week of work (ie, what you usually get) do you know the exact figure that you will get after the tax rise? Or are you guys all in the dark and just pray that the increase wont be too much?