Retirement & Tax Planning Answers
Free RMD Calculators and RMD Tax-Cost Tools
Quick answer
Four types of tools show up when people look for help with RMDs. Free IRS worksheets in Publication 590-B compute the required amount manually but say nothing about the resulting tax. Custodian calculators from firms like Fidelity, Schwab, and Vanguard automate the amount calculation for accounts held at that specific firm, but stop there. Dedicated tax-cost tools, like Singh PWM's free RMD Calculator and companion RMD Tax Cost Estimator, take the RMD amount a step further: the Calculator projects the required distribution and account balance forward through age 100 using current IRS life expectancy tables, and the Tax Cost Estimator projects the actual tax impact once that RMD is stacked with Social Security, pensions, and other income. Full financial planning software used by advisors goes furthest, running multi-year projections that account for IRMAA, bracket management, and Roth conversion tradeoffs alongside the RMD itself. Most of what shows up in a basic search only answers the easier question: how much you're required to withdraw, not what it actually costs.
There's a meaningful difference between a tool that tells you how much you're required to withdraw and one that tells you what that withdrawal actually costs in taxes. The first is a straightforward calculation: the prior year-end account balance divided by an IRS life expectancy factor. The second requires knowing your full tax picture, not just the RMD in isolation.
The IRS's own Publication 590-B includes the worksheets and life expectancy tables needed to calculate the required amount by hand, for free, but it's a manual process and offers no tax modeling whatsoever.
Custodian calculators, built into Fidelity, Schwab, Vanguard, and similar platforms, automate the amount calculation for accounts held at that specific firm. They're generally accurate for that purpose, but they typically don't factor in accounts held elsewhere, and they stop at the dollar amount owed rather than what it costs once added to the rest of a household's income.
A smaller number of tools go further and estimate the tax cost itself. Singh PWM's RMD Calculator projects both the required distribution and the account balance forward through age 100, which is useful for seeing the trajectory of RMDs over a full retirement rather than just the current year's number. The companion RMD Tax Cost Estimator takes that projected amount and models the actual tax impact once it's stacked with Social Security, pensions, and other income, which is the number that should actually drive decisions about withholding and Roth conversion timing.
The most comprehensive answer comes from the financial planning software advisors use internally, which runs a full multi-year tax projection factoring in bracket management, IRMAA thresholds, and the tradeoff between taking the RMD as computed versus converting more in earlier, lower-bracket years to shrink it in the first place.
If you're using a custodian calculator, treat the number it gives you as the required withdrawal amount, not the tax cost. Run that amount through a tax-cost tool separately before deciding on withholding.
If you hold IRAs or 401(k)s at more than one custodian, no single custodian's calculator sees the full picture. Aggregate the RMD amounts yourself, or use a tool built to project forward rather than just the current year.
Run the calculation annually, not once. The actual tax cost changes every year with income, tax law, and the account balance, not just the RMD formula.
- Assuming a custodian's RMD calculator has told you the tax bill, when it has only told you the required withdrawal amount.
- Using a single custodian's tool when RMDs are owed across accounts at multiple institutions.
- Stopping at the required withdrawal amount without checking the actual tax cost that amount creates.
- Running the calculation once and not revisiting it annually as the account balance and your age change the numbers.