Once you reach age 70 1/2, the IRS requires you to take money out of your traditional IRA, SEP IRA and SIMPLE IRA accounts. This is not required for a Roth IRA. These mandatory withdrawals are called Required Minimum Distributions (RMDs).
Required Minimum Distributions (RMDs) are not required for Roth IRAs unless you have inherited one. 
To determine your RMD, start by listing the fair market value* of your IRAs as of December 31 of the previous year. You’ll need to calculate you RMD separately for each IRA you own, but you can take your total RMD from a single IRA or a combination of IRAs.

You can use the Charles Schwab & Co., Inc., RMD Calculator at schwab.com/rmdcalculator to see the amount of your RMD based on your age, your account balance, your beneficiary, and other factors.

*Fair market value and RMD calculations may need to be adjusted to include any transfers or rollovers to your Schwab retirement  account(s), a conversion from a traditional IRA to a Roth IRA and back, or any correction for security price after year-end.

Your first RMD must be taken no later than April 1 of the year following the calendar year in which you turn age 70 1/2. Subsequent RMDs must be taken by December 31 of each year.
Once logged into your account, select the "Add/Withdraw Money" option from the menu and select to move money from your IRA account to the taxable account of your choice. Answer the remaining questions, making sure to verify the tax withholding information.
Your RMD distributions, including deductible contributions and investment earnings, are subject to federal (and possible state) income tax at ordinary income tax rates. However, distributions of any nondeductible contributions to a traditional IRA are generally free from federal tax.

You're free to withdraw more than the RMD amount, but you must pay taxes on that too. However, amounts withdrawn in excess of your annual RMD amount won’t satisfy your RMD requirements in future years. Follow the IRS guidelines and consult your tax advisor.
The taxable amount of your RMD is taxed as ordinary income at the federal income tax rate. State taxes may also apply. When you take your RMD, you can have state or federal taxes withheld immediately, or you may be able to wait until you file your taxes. Unless you give us different instructions, the IRS requires us to automatically withhold 10% of any RMD for federal income taxes.
Each year, withdrawals and any tax withholding from your tax-advantaged retirement accounts will be reported on Form 1099-R to both you and the IRS. We’re also required to notify the IRS that you must take an RMD for the year.
You may be liable for a 50% penalty on insufficient or late RMD withdrawals. Follow the IRS guidelines and consult your tax advisor