How do I calculate the minimum amount that must be withdrawn from my IRA after age 70 1/2?

You will need to get Publication 590, Individual Retirement Arrangements (IRAs) to find out this amount. Generally the minimum distribution is computed using one of three tables found in Publication 590. Table I is used by beneficiaries. Table II is for use by owners who have spouses who are more than 10 years younger. Table III is generally for use by unmarried owners and owners who have spouses who are not more than 10 years younger.