Individual Contractor. How do I do quarterly taxes?

I just recently became an individual contractor. I'm married and we file jointly. I cannot for the life of me, after days of searching irs.gov, find what percentage of my income I should be withholding and if that percentage every month should be based solely on my income or on my income minus expenses. In addition, I live in Illinois where there is state income tax and have no idea what to do there either. Please help me!!! 30%. That seems like a lot. Should it be just 15% for just me. My wife works for somebody else and her taxes are taken out at that job. Thanks Judy. All I wanted was a percentage. I already looked at the 1040ES and it means absolutely nothing to me. That doesn't help.

Public Comments

just make estimated payments. Your final tax liability will not be determined until after the tax year is over and all your exemptions, expenses, and deductions have been calculated and your adjusted gross income has been identified. Whatever you pay will be credited to your tax bill. Or you can just put a few thousand aside in an interest bearing account for use later to pay your tax bill. Good luck.
Download the packet for Form 1040-ES. http://www.irs.gov/pub/irs-pdf/f1040es.pdf I'd recommend reading the whole thing, but if you go to page 4 you'll see a little worksheet that should help you.
Without knowing your total joint income for the year, no way to even guess. But figure around 30% - that might or might not be enough but unless your joint income is over around $80K that should cover you for income tax and for federal self employment tax (for social security and medicare) Your tax as self-employed in based on your net se income after allowable expenses. You'll need to send quarterly estimated payments to the IRS (use form 1940ES) and to IL. Il is a flat 3%.
Here's something that you can do, but it may take a little time. At the end of the month before each quarterly payment (March, May, August and December) take copies of all forms you need and calculate your tax liability and deduct any payments made to date (estimates and withholding) and send in the balance with 1040 ES