Winning a million-dollar lottery jackpot doesn't mean walking away with a million dollars. State and federal taxes will slowly eat away at that windfall over time, or immediately if the payment is taken in one lump sum. The exact amount that a winner will actually receive from a lottery payout can be calculated using online calculators.

Step 1

Use the lottery payment calculator at GGuldens.org. Load the lottery payment calculator into your browser and scroll to the bottom of the page. Enter the total amount of money from the lottery payout before taxes and the number of years during which the prize will be paid out. Enter the percentage of taxes to be withheld in your state and click "Calculate." The boxes below this section of the page will fill with information on the amount a winner will receive from annual payments as opposed to a lump-sum cash payment.

Step 2

Use the Powerball/Mega Millions calculator on DavidWeir.com. This calculator is designed specifically for the Powerball and Mega Millions lottery games. Click the box next to the appropriate game from the top of the screen. Enter the total amount of prize money into the box and click "Calculate" to view the amount a winner would receive annually or in a lump sum.

Step 3

Go through the "Jackpot Analysis" pages on USA Mega.com, which provides detailed breakdowns of monetary prizes for the Mega Millions and Powerball multistate lottery games. Each analysis page shows how much a winner would take home in a lump sum and the annual prize amounts for each state. Taxes are taken into account for these totals. These pages are recalculated every time a new jackpot amount is available.