Robert Samuelson has the numbers:
Obama’s still-vague Buffett Tax would apparently impose a minimum 30 percent tax rate on incomes exceeding $1 million....In September, the Congressional Budget Office estimated the 10-year deficit at $8.5 trillion. The nonpartisan Tax Foundation estimates that a Buffett Tax might now raise $40 billion annually. Citizens for Tax Justice, a liberal group, estimates $50 billion. With economic growth, the 10-year total might optimistically be $600 billion to $700 billion. It would be a tiny help; that’s all.