Rates are set by fiscal year, effective October 1 each year. Find current rates in the continental United States ("CONUS Rates").
If you're self-employed and also have a job you can avoid having to make estimated federal tax payments.
An employee who does not expect any other taxable income for the current tax year, other than his salary, and does not expect to owe $1,000 or more AFTER subtracting federal income taxes withheld and any tax credits, generally will not have to pay estimated taxes for the current tax year.
If you pay at least 90% of the current year's tax liability or 100% of the previous year's tax liability, you won't be required to pay estimated taxes.