Best Retirement Calculators Compared (2026): Why They Give Different Answers

Type "retirement calculator" into a search bar and you'll get a dozen tools that all claim to answer the same question: will your money last? Enter the same numbers into Empower, NerdWallet, and cFIREsim and you can get three different answers, sometimes wildly different ones. That's not a bug in any of them. It's because "will your money last" isn't actually one question. It's three, and each tool below answers a different version of it. This guide reviews ten of the most-used retirement calculators against transparent criteria, groups them by what they're actually built to do, and includes a tool that runs your own numbers through the three core methodologies at once so you can see the disagreement for yourself instead of taking any single tool's word for it.

The three methodologies

Every calculator in this comparison uses one of three underlying approaches, and the approach matters more than the brand name on the tool.

Fixed-rate projection assumes one average return every year with no variation. It's the simplest method and the fastest to compute, which is why it powers most of the free, no-signup calculators built for quick estimates. Its structural weakness is that real markets never return the same amount every year, and a fixed-rate model can't capture sequence-of-returns risk, the fact that a market crash in the first years of retirement does far more damage than the identical crash a decade in, because there's less time left for the portfolio to recover before withdrawals resume.

Monte Carlo simulation runs a plan through thousands of randomized market scenarios, each one a different possible sequence of annual returns drawn from historical data, and reports the share of those scenarios where the money lasted. It converts "will it last" from a single pass-or-fail answer into a probability, which is a genuinely better question to ask. Its limitation is that a randomized sequence, however statistically grounded, isn't a real sequence of years that happened.

Historical backtesting sidesteps that limitation by testing a plan against every real consecutive stretch of actual market history instead of a randomized one. A 30-year backtest checks the plan against every real 30-year window available in the data, including the ones that started right before 1929, 1937, 1966, 1973, or 2008. It's the most grounded of the three methods and the one fewest calculators use, but it's limited to the one sample of market history that actually happened.

Run the same plan through all three at once, side by side, with an explanation of why the answers differ:

Zero-signup Monte Carlo: Vanguard and T. Rowe Price

Vanguard's Retirement Nest Egg Calculator is fully anonymous, asks for almost nothing beyond a balance, a spending rate, and an asset mix, and runs a genuine 5,000-trial Monte Carlo simulation drawing from historical stock and bond returns. It's fast and transparent, but bare-bones by modern standards: no Social Security, no tax modeling, no multiple accounts, and no income sources beyond the portfolio itself.

T. Rowe Price's Retirement Income Calculator is guest-usable with no signup required and runs a proprietary Monte Carlo simulation across roughly 1,000 scenarios using the firm's own capital-market assumptions. It goes further than Vanguard on inputs, supporting multiple account types, Social Security, and other income sources, and it projects an actual monthly income stream through retirement rather than a bare pass-or-fail score. The tradeoff is that its capital-market assumptions are a black box relative to Vanguard's disclosed historical-return method.

Account-linked precision: Empower and Fidelity

Empower's Retirement Planner requires linking your bank, brokerage, and retirement accounts through Plaid, and in exchange runs roughly 5,000 Monte Carlo simulations against your actual, real-time linked balances rather than manually entered estimates. The realism is the product. It's also, by design, a lead funnel into Empower's paid wealth-management advisory service, so the "free" framing carries a sales layer behind it.

Fidelity's tools are split: a standalone Retirement Score is usable without logging in, while the fuller Planning & Guidance Center and myOrangeMoney require a Fidelity or NetBenefits login and are largely scoped to accounts held at Fidelity. The underlying Monte Carlo simulation runs a minimum of 250 scenarios explicitly modeled under below-average market conditions rather than average ones, and produces a color-banded on-track score that's unusually easy to read at a glance. Full functionality, though, is tied to a Fidelity account relationship rather than being a neutral, all-accounts tool.

Historical backtesting: cFIREsim and ficalc.app

cFIREsim requires no signup and tests a plan against every rolling U.S. market period since 1871, including stocks, bonds, gold, and inflation, with optional withdrawal strategies beyond a flat percentage. Its standout feature is a cycle view showing exactly which historical start years failed and why, which builds more trust than a single success percentage. The project has also been reported to have maintenance issues, including a stalled rewrite and documented data bugs, and its interface hasn't kept pace with newer tools.

ficalc.app mirrors cFIREsim's historical-backtest approach in a cleaner, more modern interface, and is free with no signup. It's also the narrowest tool in this comparison: no tax modeling, no Social Security handling, and no Monte Carlo option, maintained by a single developer as a side project.

Comprehensive DIY planning: Boldin and ProjectionLab

Boldin, formerly NewRetirement, offers a free tier covering broad net-worth and cash-flow modeling across more than 250 inputs, including Social Security, pensions, healthcare, and state taxes. Its real Monte Carlo simulation and detailed tax modeling are gated behind a $12 to $14 a month PlannerPlus subscription, and the sheer input count can overwhelm a casual user looking for a quick answer.

ProjectionLab combines Monte Carlo simulation and historical backtesting with a visualization-first interface, including Sankey cash-flow charts and a side-by-side scenario comparison mode. A free tier covers the core planning tools; the paid tier is annual-billing only, with no monthly option, and there's no automatic account syncing, so every balance is entered by hand.

Free all-in-one: RetirePro

RetirePro runs a roughly 1,000-scenario Monte Carlo simulation combined with real tax modeling, including RMDs and Roth conversions, plus a Social Security claiming optimizer, all free with no signup and no account linking. Bundling Monte Carlo, tax modeling, and Social Security optimization without a paywall is unusual among the tools reviewed here. It's also a newer, less-established brand than cFIREsim or Boldin, and its free tier caps out at three accounts, which limits how much of a real household it can model.

Quick estimates: NerdWallet and SmartAsset

NerdWallet's retirement calculator is fully anonymous and fast, using a fixed rate-of-return projection rather than Monte Carlo or historical backtesting. It gives a single deterministic number with no probability attached, and Social Security only enters as a lumped "other income" catch-all rather than its own input. Its real strength is content and SEO integration with NerdWallet's broader site, not calculation depth.

SmartAsset's retirement calculator also uses a fixed rate-of-return projection, with one genuine edge over NerdWallet: it models state-level tax impact on retirement income alongside pensions and Social Security. The tool functions as a lead-generation funnel into SmartAsset's advisor-matching business, which has documented Better Business Bureau complaints about lead quality, separate from the calculator's own math.

Where SwitchWize fits

SwitchWize's retirement calculators run a genuine Monte Carlo simulation and a historical backtest, both drawn from the same 1928-to-present dataset used above, layered onto calculators that already model IRMAA thresholds, a Medicare COBRA-to-ACA coverage bridge, a Roth-conversion corridor sized against RMDs and IRMAA simultaneously, and a household Social Security spousal claiming strategy, a tax and household planning depth none of the ten tools above match. All of it runs in the browser: no account linking, no signup, and no balance or withdrawal figure is ever sent anywhere. The one thing offered here that nothing above does is running all three methodologies on the same numbers at once, so the disagreement between them is visible instead of hidden behind a single score. Every SwitchWize calculator is also embeddable on another site directly, something none of the ten tools reviewed here provide.

At a glance

Run your own numbers through all three methods above, or start with the underlying retirement planning suite: