Every retirement calculator answers a question. The trouble is that the question is rarely the one you asked. You typed in your portfolio and your age and your spending; the calculator answered a different question — usually some version of “what is the probability that this nest egg survives until age 95, assuming the next forty years look like the last hundred?” That is a real question. It is not, for most readers of this site, the question.
Below are five of the tools people actually use. Each one does something well. Each one hides something. The hidden part is usually the assumption about how long you intend to be alive.
1. NewRetirement / Boldin
NewRetirement, recently rebranded as Boldin, is the most thorough mainstream planner. It models taxes properly — Roth conversion ladders, IRMAA cliffs, RMDs, state-level treatment — at a depth no spreadsheet you’ll build can match. If your retirement plan touches the US tax code in a non-trivial way, this is the tool. The paid tier (around $120/year as of 2026) is one of the few software subscriptions in this space that returns its cost in the first hour of use.
What it hides: the default end-of-plan age is 95, and the UI nudges you to leave it there. Set it to 75 and the entire plan loosens by 30%. The tool will let you do this, but it won’t suggest you do, and the dashboard’s “probability of success” metric is calibrated to that ninety-five-year endpoint. The number is real arithmetic. It is also answering a question that quietly assumes you’d like to be eating hospital food at 94.
When to use it: late in your planning, once you’ve decided your horizon. Not first. Boldin is a precision instrument; bring it your assumptions, don’t let it set them.
2. cFIREsim
cFIREsim runs your portfolio against every starting year in US market history since 1871 and tells you the percentage of cycles your money survived. This is the Monte Carlo your spreadsheet wishes it were. It is also the tool that taught a generation of FIRE planners the phrase sequence-of-returns risk — the observation that two retirees with identical average returns can land in radically different places depending on the order in which the bad years arrive.
What it hides: the past is not the future, and US-only history is a survivor-biased sample. The 96% success rate cFIREsim reports for a 4% withdrawal is a statement about American capitalism between Grant and Biden. Whether it survives the next forty years is a separate question. The other quiet bias: the tool defaults to “constant inflation-adjusted withdrawal,” which nobody actually does. Real retirees flex their spending. Real-world success rates are higher than cFIREsim shows, in ways the tool doesn’t quite credit.
When to use it: for stress-testing, not target-setting. Run your number through it; don’t let it pick your number.
3. Engaging-Data’s Retirement Calculator
The Engaging-Data calculator — the Rich, Broke, or Dead tool by data designer Eric Roston and collaborators — is the only one on this list that makes mortality visible. It shows you, in a grid of dots, the probability you are dead before the money runs out. Each year is a square; the green squares are years your portfolio survives, the gray squares are years you don’t. Once you have seen the grid, the other calculators feel slightly dishonest, because they have been showing you the green squares and quietly hiding the gray.
What it hides: almost nothing, which is why it’s on this list. It uses SSA actuarial tables and lets you adjust them for your own honesty about smoking, sex, and family history. The one limitation is the interface, which is more spartan than the consumer tools — there is no soft Roth-conversion modeling here.
When to use it: first. Always first. Use the Engaging-Data tool to ground every other number you generate. If you skip it, every subsequent calculator will assume you’d like to be eighty-eight.
4. Fidelity Retirement Score
Fidelity’s tool gives you a score out of 150 and a colored dial. Green means on track. Yellow means more contributions, please. The thing it never tells you is that the calculation assumes you will keep your money at Fidelity and keep contributing on Fidelity’s recommended schedule.
What it hides: its function. The Retirement Score is a sales surface for Fidelity’s managed products, dressed as a planning tool. The math is reasonable; the framing is not.
When to use it: never as a primary source. Useful as a sanity check if you already have Fidelity accounts and want a quick read on whether their model thinks you’re insane.
5. Portfolio Visualizer
Portfolio Visualizer is the closest thing the retail investor has to an institutional research terminal. Backtest any allocation against any window since 1972. Run Monte Carlo on your specific portfolio. Model factor tilts — small-cap value, momentum, quality. Compare two strategies side by side with rolling-return charts that would have cost a Bloomberg subscription a decade ago. It is genuinely excellent.
What it hides: the tool that gives you this much power gives you exactly enough to over-fit. If you run forty backtests, one of them will look amazing. That one is the one you’ll remember, and the one whose 9.4% historical CAGR will quietly become your planning assumption. Portfolio Visualizer punishes the user who treats it as a search engine for the optimal allocation. The 1972 starting date is also not innocent — it begins inside a fifty-year window in which US equities did extraordinarily well by global and historical standards.
When to use it: to validate an allocation you arrived at for principled reasons, or to understand the historical character of a strategy you already plan to follow. Not to discover one, and never to choose between forty.
A summary, with reservations
| Tool | Best at | Worst lie |
|---|---|---|
| Boldin | Tax modeling | Default age 95 |
| cFIREsim | Historical stress-testing | US history = future |
| Engaging-Data | Showing mortality | (Almost none) |
| Fidelity | Quick sanity check | Sales surface in disguise |
| Portfolio Visualizer | Backtests | Tempts you to over-fit |
Use two of these together, never one alone. The pair that catches the most lies is Engaging-Data plus Boldin: one tells you when you’ll likely be dead, the other tells you what the tax code will do to you on the way there.
The calculator is not the plan. The plan is the conversation with yourself that the calculator forces you to have, the one that begins with how long you intend to be present and ends with a number you can defend out loud. The tools are only as honest as the inputs. The most important input is the year you stop pretending you’ll live to 95.
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