In short: SimpleRMD calculates your Required Minimum Distribution by dividing your prior year-end account balance by the applicable IRS life expectancy factor from Publication 590-B. It uses the exact tables published by the IRS — Uniform Lifetime (Table III), Joint Life and Last Survivor (Table II), or Single Life Expectancy (Table I) — depending on your situation. No proprietary formulas. No rounding. No estimation.
On this page
- The Formula
- Where the Numbers Come From
- How the Calculator Selects Your Table
- What "Updated for 2026" Means
- Inherited IRA Logic
- Multiple Accounts and Aggregation
- What the Calculator Does Not Do
- How to Verify the Result Yourself
- Common Sources of Discrepancies
- Frequently Asked Questions
If you're trusting a calculator with something that carries a 25% IRS penalty for getting wrong, you should know exactly how it works. Fair question. Here's the full answer.
SimpleRMD uses the same formula and the same IRS tables that your tax professional would use if they calculated your RMD by hand. There is no proprietary algorithm, no "estimate," and no rounding shortcut. The calculator takes your inputs, selects the correct IRS life expectancy table, looks up your factor, and divides. That's it.
This page shows you the methodology — every step, every source, every assumption. If anything here doesn't match what your CPA would do, we want to know.
The Formula
Every RMD calculation — whether done by hand, by a CPA, or by this calculator — uses the same formula:
RMD = Prior year-end account balance (Dec. 31) ÷ IRS life expectancy factor
That's the entire calculation. There is no weighting, no adjustment, and no intermediate step. The complexity isn't in the math — it's in making sure you have the right balance, the right table, and the right factor.
SimpleRMD does not modify or approximate the IRS factors. The factor for a 76-year-old on the Uniform Lifetime Table is 23.7. The calculator divides by 23.7. If the result is $14,767.932…, the calculator displays $14,767.93.
Where the Numbers Come From
The life expectancy tables used by SimpleRMD come from a single source:
IRS Publication 590-B, Appendix B — available on IRS.gov
This publication contains three tables:
- Table III (Uniform Lifetime Table) — used by most original account owners.
- Table II (Joint Life and Last Survivor Table) — used when the sole beneficiary is a spouse more than 10 years younger.
- Table I (Single Life Expectancy Table) — used by beneficiaries of inherited IRAs.
All three tables were updated effective January 1, 2022 (Treasury Decision 9930), replacing the previous tables that had been in effect since 2002. The current tables reflect longer life expectancies, which means slightly larger factors and slightly smaller RMDs at every age.
SimpleRMD uses the 2022-revised tables. These are the current tables and have not been revised since.
For a full walkthrough of each table, including representative factors and worked examples: IRS RMD tables explained
How the Calculator Selects Your Table
Table selection is one of the most common places for manual errors. SimpleRMD determines which table to use based on your inputs:
If you own the account (not inherited):
- Default: Uniform Lifetime Table (Table III)
- Exception: If you indicate that your sole beneficiary is your spouse and your spouse is more than 10 years younger, the calculator switches to the Joint Life and Last Survivor Table (Table II). This produces a larger factor and a smaller RMD.
If you inherited the account:
- The calculator uses the Single Life Expectancy Table (Table I).
- If the original owner had already reached their required beginning date before death, annual RMDs are required during the 10-year window. The calculator applies the factor-reduction method: initial factor based on your age in the year after the owner's death, reduced by 1 each subsequent year.
- If the original owner died before their required beginning date, the calculator follows the applicable distribution rules for your beneficiary type.
You don't need to know which table is correct — the calculator figures it out from your answers. But if you want to understand the logic: Which table do you use?
Comparison showing how SimpleRMD calculator methodology aligns with IRS Publication 590-B tables and formulas.
What "Updated for 2026" Means
When we say the calculator is "updated for 2026," we mean three things:
The tables are current. The IRS life expectancy factors used are the 2022-revised tables from Pub 590-B, which remain in effect for 2026 distribution calculations. If the IRS revises the tables in the future, SimpleRMD will update them before the new tables take effect.
The age logic is current. The calculator uses the RMD starting ages set by SECURE 2.0: age 73 for those born 1951–1959, and age 75 for those born in 1960 or later (effective in 2033). If you haven't yet reached RMD age, the calculator will tell you.
The inherited IRA rules are current. The calculator reflects the final IRS regulations issued in July 2024 (T.D. 10001), including the requirement for annual distributions during the 10-year window when the original owner died after their required beginning date. The penalty waiver for missed inherited IRA distributions in 2021–2024 has ended — the calculator does not assume any waiver applies.
What "updated" does not mean: we do not change anything that the IRS hasn't changed. The underlying math hasn't changed since 2022. If you run the same inputs today that you ran last year, you'll get the same factor — your balance and age are the only things that changed.
Inherited IRA Logic
Inherited IRAs are the most complex scenario the calculator handles. Here's what it does:
Determines beneficiary type. Based on your inputs, the calculator identifies whether you are an eligible designated beneficiary (spouse, minor child, disabled/chronically ill, or someone not more than 10 years younger than the deceased), a designated beneficiary (most adult children, siblings, friends), or a non-designated beneficiary (estate, charity, certain trusts).
Applies the correct distribution rule. Designated beneficiaries are subject to the 10-year rule. Whether annual RMDs are required during those 10 years depends on whether the original owner had started taking their own RMDs. The calculator asks the questions needed to make this determination.
Uses the correct factor method. For beneficiaries who must take annual distributions, the calculator looks up the initial Single Life factor based on age in the year after the owner's death, then subtracts 1 for each subsequent year. It does not do a fresh table lookup each year — that would produce a slightly different (and incorrect) result.
Tracks the 10-year deadline. The calculator shows the year by which the entire account must be emptied.
For the full rules: Inherited IRA RMD rules · The 10-year rule explained
Multiple Accounts and Aggregation
If you have more than one retirement account, the calculator handles each one separately — because the IRS requires a separate RMD calculation for each account.
The aggregation rules are built in:
- Multiple IRAs: The calculator shows the total IRA RMD and notes that you may withdraw the combined amount from any one (or combination) of your IRAs.
- Multiple 401(k)s: Each plan's RMD must be taken from that specific plan. The calculator shows each amount individually.
- Multiple 403(b)s: Can be aggregated with other 403(b)s, but not with IRAs or other plan types.
- Inherited IRAs: Cannot be aggregated with your own IRA RMDs. Calculated and displayed separately.
This matters because aggregation mistakes are one of the most common reasons people accidentally under-distribute — and a shortfall is treated the same as a missed RMD.
Related: RMDs by account type
What the Calculator Does Not Do
Transparency means being clear about scope. Here's what SimpleRMD does not do — by design, not by oversight:
Does not estimate your tax liability. Your RMD is taxable income, but how much tax you owe depends on your total income, filing status, deductions, and state tax rules. That's your CPA's territory. For an educational overview: How much tax will you owe on your RMD?
Does not recommend withholding amounts. You can choose how much federal (and sometimes state) tax to withhold when you take a distribution. The calculator doesn't suggest a withholding percentage — that decision depends on your full tax picture.
Does not account for Qualified Charitable Distributions (QCDs). A QCD can satisfy part or all of your RMD while reducing taxable income, but it involves coordination between you, your custodian, and the charity. The calculator shows what you owe — how you satisfy it is between you and your tax professional.
Does not provide financial or investment advice. SimpleRMD tells you the minimum amount you must withdraw. It does not suggest when to take it, where to reinvest it, or how to structure distributions across accounts for tax efficiency.
Does not replace your CPA. The calculator gives you the number. Your tax professional gives you the context. For many people, the most useful thing SimpleRMD does is produce a CPA-ready PDF export that gives your accountant the inputs, the math, and the result — so you're not starting from scratch every April.
How to Verify the Result Yourself
You should be able to check this. Here's how:
Step 1: Find your prior year-end account balance (December 31 of last year). This appears on your year-end statement or on Form 5498 from your custodian.
Step 2: Determine your age as of December 31 of the current year.
Step 3: Look up your life expectancy factor in the appropriate table in IRS Publication 590-B, Appendix B. If you're not sure which table to use: which table applies to you?
Step 4: Divide balance by factor.
The result should match what SimpleRMD shows. If it doesn't, check that you're using the same age (as of Dec. 31, not your current age), the same balance (prior year-end, not current), and the correct table. These are the three most common sources of discrepancy.
Common Sources of Discrepancies
If your number doesn't match a number from another source — your broker's estimate, another calculator, or a figure your CPA provided — here are the usual reasons:
Different balance date. SimpleRMD uses the December 31 prior-year balance, which is what the IRS requires. Some custodian estimates use a more recent balance, which will produce a different number.
Wrong age reference. The IRS uses your age as of December 31 of the distribution year. If a calculator uses your current age or your age at the start of the year, the factor may be off by one.
Old tables. Any calculator, spreadsheet, or reference published before 2022 may be using the pre-2022 life expectancy tables. The old tables have smaller factors, which produce larger RMDs. If your number is slightly higher than what SimpleRMD shows, old tables are likely the reason.
Joint Life Table not applied. If your sole beneficiary is a spouse more than 10 years younger, you should be using Table II. If another calculator defaults to the Uniform Table without asking about your beneficiary, it will overstate your RMD.
Inherited IRA factor method. For designated beneficiaries under the 10-year rule, the factor should be reduced by 1 each year from the initial lookup — not recalculated fresh each year. A fresh lookup produces a slightly different (and incorrect) factor.
If you find a discrepancy you can't explain, we'd genuinely like to hear about it. Accuracy is the entire point.
Frequently Asked Questions
Does SimpleRMD use the same tables as my broker?
It should. Every RMD calculation — whether performed by Fidelity, Schwab, Vanguard, a CPA, or SimpleRMD — is based on the same IRS tables from Publication 590-B. The differences between tools usually come down to which table they select for your situation, what balance they use, and how they handle edge cases like inherited IRAs. The underlying factors are identical. If your broker's estimate doesn't match, see common sources of discrepancies above — the usual culprits are balance date, age reference, or table defaults.
What happens when the IRS changes the tables?
SimpleRMD will update its tables before the new tables take effect for distribution calculations. The last table revision was effective January 1, 2022. There is no scheduled revision at this time. When a change does happen, every affected article on this site will be updated and re-dated.
Can I rely on this calculator instead of a CPA?
For the RMD number itself — the minimum amount you need to withdraw — the calculator uses the same formula and tables your CPA would. But an RMD calculation is only one piece of your annual tax picture. Your CPA considers withholding, estimated payments, other income sources, deductions, and state taxes. SimpleRMD handles the calculation; your tax professional handles the strategy. Many of our users run the calculator first, then bring the exported PDF to their CPA to save time and confirm the number.
Is the calculator free?
Yes. The RMD calculation is free, requires no account, and shows the full result. The paid plan ($99/year) adds saved inputs, multi-account dashboards, deadline reminders, and CPA-ready PDF exports — but the core calculation is always free.
How do I report an error?
If you believe the calculator has produced an incorrect result, please contact us. Include the inputs you used and the result you expected. We take accuracy reports seriously — if there's a bug, we want to find it before it affects anyone else.
Ready to run the numbers?
- Try the calculator — free, no account required
- See how SimpleRMD works
- IRS RMD tables explained
- What information do you need to calculate your RMD?
This article is for informational purposes only and does not constitute tax, legal, or financial advice. IRS rules and tax laws are subject to change. Consult a qualified tax professional or financial advisor for guidance specific to your situation. SimpleRMD is a calculation and tracking tool — not a financial advisory service.
Sources: IRS.gov (Publication 590-B, HTML · Publication 590-B, PDF · Retirement Topics: RMDs). Life expectancy tables per T.D. 9930, effective January 1, 2022. Inherited IRA rules per Final Regulations T.D. 10001, effective for distributions in 2025 and later. Methodology confirmed current as of February 2026.