To calculate a required minimum distribution, divide your retirement account balance as of December 31 of the previous year by the life expectancy factor the IRS assigns to your current age. That single division gives you the dollar amount you must withdraw for the year. The math is straightforward, but choosing the right table, using the correct balance, and handling multiple accounts require attention to detail.
The Basic Formula
Every RMD calculation follows the same structure:
Prior year-end balance ÷ IRS life expectancy factor = RMD
For example, if your traditional IRA held $500,000 on December 31 of last year and the IRS table gives you a life expectancy factor of 26.5, your RMD for this year is $500,000 ÷ 26.5 = $18,868. You can always withdraw more than this amount, but you cannot withdraw less without facing a penalty.
When RMDs Begin
You generally must start taking RMDs from traditional IRAs, SEP IRAs, SIMPLE IRAs, 401(k)s, 403(b)s, and other defined contribution plans when you reach age 73. Your first RMD is due by April 1 of the year after you turn 73. Every RMD after that is due by December 31 of each year. If you delay your first distribution to that April 1 deadline, you will owe two RMDs in the same calendar year (one for the prior year and one for the current year), which could push you into a higher tax bracket.
If you’re still working and participate in a 401(k) or similar employer plan, some plans let you delay RMDs until the year you actually retire, as long as you don’t own 5% or more of the company. This exception does not apply to IRAs.
Which IRS Table to Use
The IRS publishes life expectancy tables in Publication 590-B. Most people use the Uniform Lifetime Table, which lists a divisor for each age starting at 72. The divisor shrinks as you get older, meaning your RMD percentage grows each year.
There is one situation where you use a different table. If your sole beneficiary is a spouse who is more than 10 years younger than you, you use the Joint Life and Last Survivor Expectancy Table instead. That table produces a larger divisor (longer life expectancy), which results in a smaller required withdrawal. If your beneficiary is anyone else, or if you have multiple beneficiaries, you stick with the Uniform Lifetime Table.
Getting the Account Balance Right
The balance you use is always the fair market value of the account on December 31 of the year before the distribution year. If you’re calculating your 2025 RMD, you use your account balance from December 31, 2024. Your brokerage or plan custodian typically reports this figure on IRS Form 5498, which arrives in the spring.
If you made a rollover into the account late in the prior year, that amount is included in the December 31 balance and factors into your RMD. Conversely, if you converted part of a traditional IRA to a Roth during the prior year, that converted amount is no longer in the traditional IRA balance, so it reduces your RMD.
Handling Multiple Accounts
If you own more than one retirement account, the aggregation rules depend on the account type:
- Traditional IRAs (including SEP and SIMPLE IRAs): Calculate the RMD separately for each IRA, then add the amounts together. You can withdraw the combined total from any one IRA or split it across several. This flexibility lets you draw from whichever account is most convenient or tax-efficient.
- 403(b) accounts: Same rule as IRAs. Calculate each account’s RMD separately, but you can take the total from one or more of your 403(b) contracts.
- 401(k) and 457(b) plans: Each plan’s RMD must be taken from that specific plan. You cannot satisfy a 401(k) RMD by withdrawing extra from your IRA, or combine two 401(k) RMDs and pull from just one plan.
You also cannot mix account types. An IRA RMD cannot be satisfied by a withdrawal from a 403(b), or vice versa.
A Step-by-Step Example
Say you’re 75 years old and own two traditional IRAs. IRA #1 had a balance of $300,000 on December 31 of the prior year, and IRA #2 had $200,000. The Uniform Lifetime Table divisor for age 75 is 24.6.
IRA #1 RMD: $300,000 ÷ 24.6 = $12,195
IRA #2 RMD: $200,000 ÷ 24.6 = $8,130
Your total RMD across both IRAs is $20,325. You could withdraw $20,325 entirely from IRA #1, entirely from IRA #2, or split it any way you choose, as long as the combined withdrawal meets or exceeds $20,325 by December 31.
Inherited Account Calculations
If you inherited a retirement account, the calculation rules change depending on your relationship to the original owner and when they died.
Most non-spouse beneficiaries who inherited an account after 2019 fall under the 10-year rule: you must empty the entire account by December 31 of the year containing the 10th anniversary of the owner’s death. If the owner died in 2025, for instance, the account must be fully distributed by December 31, 2035. If the owner had already begun taking RMDs before death, you may also need to take annual distributions during those 10 years.
Certain beneficiaries qualify as “eligible designated beneficiaries” and can stretch distributions over their own life expectancy instead of following the 10-year rule. This group includes the surviving spouse, a minor child of the owner, someone who is disabled or chronically ill, and anyone no more than 10 years younger than the original owner. These beneficiaries use the Single Life Expectancy Table (Table I in Publication 590-B), finding their age-based factor in the year after the owner’s death and reducing that factor by one for each subsequent year.
Surviving spouses have the most flexibility. They can roll the inherited account into their own IRA and treat it as theirs, delaying RMDs until they reach age 73. Or they can keep it as an inherited IRA and use the Single Life Expectancy Table, recalculating their factor each year based on their current age rather than reducing it by one annually.
The Penalty for Getting It Wrong
If you withdraw less than the required amount, the IRS imposes an excise tax of 25% on the shortfall. That penalty drops to 10% if you correct the mistake within two years by taking the missed distribution and filing an updated tax return. On a $20,000 RMD that you forgot entirely, the 25% penalty would cost you $5,000, or $2,000 if corrected quickly.
For plan-level failures (where an employer plan failed to process distributions), the plan sponsor can apply to the IRS Voluntary Correction Program using Form 14568 and Schedule 8 to request a waiver of the excise tax. Individual IRA owners correct the error by simply taking the missed distribution and filing Form 5329 with their tax return.
Roth Accounts and RMDs
Roth IRAs do not require RMDs during the owner’s lifetime. If you have money in a Roth IRA, you can leave it untouched for as long as you live. However, Roth 401(k) accounts were previously subject to RMDs. Starting in 2024, Roth 401(k)s are also exempt from RMDs, matching the Roth IRA rule. If you hold a Roth 401(k), you no longer need to factor it into your calculations.
Beneficiaries who inherit a Roth IRA still need to follow distribution rules (typically the 10-year rule for non-eligible designated beneficiaries), even though those distributions come out tax-free.