Best Free FIRE Calculators 2026: 11 Tools Compared (Including Ours)

The FIRE calculator landscape has evolved significantly. You can now do everything from a quick FIRE number estimate to full Monte Carlo simulation to complete tax-optimized retirement modeling — much of it free.

Here's an honest comparison of the tools we tested, including our own, ranked by what each one does best.

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Quick Reference: Which Calculator to Use

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Free FIRE Calculators — Full Reviews

1. InvestToFire FIRE Calculator — Best for Pension & Government Employee FIRE

URL: investtofire.com/calculators/fire Cost: Free, no signup

The InvestToFire FIRE Calculator is the only free calculator with a dedicated pension / VA income / side income field that reduces your required FIRE number. This matters for three large audiences that other calculators ignore:

• Federal employees with FERS pensions
• Teachers with state pension income
• Military veterans with military pension or VA disability payments

Standard FIRE calculators assume all income comes from the portfolio. Enter a $20,000/year pension and the calculator adjusts: instead of needing $1,500,000 for $60,000/year spending, you need $1,000,000. That's a 33% reduction in required savings.

Other features: Lean FIRE / Fat FIRE / Chubby FIRE / Coast FIRE scenario modeling, savings rate display, and visual timeline.

Best for: Federal employees, teachers, military, and anyone with guaranteed income that reduces their FIRE number.

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2. InvestToFire Coast FIRE Calculator — Best Free Coast FIRE Tool

URL: investtofire.com/calculators/coast-fire Cost: Free, no signup

Coast FIRE is the inflection point where your portfolio, with zero additional contributions, will compound to your full FIRE number by your target retirement age. The InvestToFire Coast FIRE Calculator is clean, focused, and shows you exactly how much you've coasted vs. how much further you need to go.

Best for: Early career savers wondering if they can ease off the savings accelerator.

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3. FIRECalc — Best for Historical Failure Rate Testing

URL: firecalc.com Cost: Free

FIRECalc is one of the original FIRE calculators. It tests your retirement plan against every rolling period in market history going back to 1871 and tells you what percentage of those periods succeeded. If you want to know whether your withdrawal rate held up during the Great Depression, the 1970s stagflation, and 2000–2002 combined — FIRECalc is the tool.

What it does: Historical success rate testing (not Monte Carlo). Simple input: portfolio size, spending, retirement length.

Limitation: The interface is dated; no pension income field; no visual breakdown of expenses vs. income.

Best for: Sanity-checking your safe withdrawal rate against history. Run this alongside whatever other calculator you use as a second opinion.

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4. cFIREsim / FIREproof — Best Free Monte Carlo

URL: cfiresim.com Cost: Free

Originally built by a moderator of r/financialindependence, cFIREsim (now evolving under the FIREproof brand) offers Monte Carlo simulation, basic tax calculations, and ACA subsidy modeling. It has 14+ years of community trust and a strong feature set for a free tool.

What it does: Monte Carlo simulation, basic tax modeling, ACA subsidy estimates, flexible withdrawal strategies.

Limitation: UI is functional but not polished; some advanced features require navigating multiple tabs.

Best for: Intermediate FIRE planners who want probability-based output rather than historical-only testing.

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5. firenum — Best Free Tool for Life-Event Modeling and Non-USD Planning

URL: firenum.com Cost: Free, no signup

firenum is the closest a free tool currently gets to the paid planners. Instead of a single spending figure, it models your finances month by month: dated life events (home purchase, inheritance, career change), income and expense streams that each carry their own inflation and growth rate, and 9 account types including 401(k), IRA, Roth, HSA, brokerage, real estate, and crypto. Withdrawals follow one of three orderings — tax-efficient, proportional, or custom — with the 59½ early-withdrawal rules built in.

What it does: Monte Carlo (10,000 simulations, drift-corrected lognormal) plus historical backtesting against the Shiller S&P 500 dataset going back to 1871, six one-click stress tests (market crash, job loss, expense spike, high inflation, retiring early, retiring late), CSV export, shareable URLs, and an Android install.

The differentiator: 9 currencies and 8 country locales. Almost every free FIRE calculator — ours included — silently assumes you are American and paid in dollars. If you are running FIRE numbers in euros, pounds, rupees, or yen, this is the free tool to use. It also runs entirely in the browser with your numbers stored in localStorage, so nothing is uploaded and there is no account to create.

Limitations: The backtesting engine is US market history even when the display currency is not, so a UK or EU planner is still borrowing US return sequences. There is no full federal or state tax-return modeling the way ProjectionLab does it — withdrawal ordering is tax-aware, but it is not a tax engine. And because state lives in your browser, there is no sync between your laptop and your phone; you export and re-import.

Best for: Anyone whose plan has moving parts — a house purchase, a career break, an inheritance — and anyone planning FIRE outside the United States.

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6. WalletBurst FIRE Calculator

URL: walletburst.com/tools/fire-calculator/ Cost: Free

WalletBurst offers a clean, visual FIRE calculator with a nice chart showing portfolio growth toward your FIRE number. It's fast and intuitive for a first-pass estimate.

Limitation: No pension income field; no Monte Carlo; relatively basic compared to the above.

Best for: Beginners who want a visual, approachable first look at their FIRE number.

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7. NerdWallet FIRE Number Calculator

URL: nerdwallet.com Cost: Free

NerdWallet's FIRE calculator is the most accessible entry point for people new to the concept — it explains the 4% rule and FIRE number as you use it. Clean, mobile-friendly, and well-integrated with NerdWallet's wider personal finance content.

Limitation: Very basic; no portfolio survival testing, no pension support, no withdrawal strategy modeling.

Best for: Absolute beginners who haven't encountered FIRE before.

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8. The FI Calculator

URL: theficalculator.com Cost: Free

The FI Calculator emphasizes stress-testing: it simulates portfolio survival including market crashes and life events. It also includes an AI retirement chatbot that can model scenario questions conversationally.

Best for: Users who want scenario modeling with a conversational interface.

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9. InvestingFIRE

URL: investingfire.com Cost: Free

InvestingFIRE combines FIRE number calculation with Monte Carlo simulation in a single clean tool. Inputs include current portfolio, savings rate, expected returns, target spending, inflation, and withdrawal rate — it outputs projected FIRE age and portfolio survival probability.

Best for: Users who want Monte Carlo in a simpler interface than cFIREsim.

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10. Playing With FIRE Retirement Calculator

URL: playingwithfire.co/retirementcalculator Cost: Free

The Playing With FIRE calculator (companion to the FIRE documentary) is clean and designed for a general audience. Straightforward FIRE number and timeline estimate.

Best for: People introduced to FIRE through the documentary who want a quick calculation.

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Paid Tools Worth Considering

ProjectionLab — Best Full-Featured FIRE Tool (Paid)

URL: projectionlab.com Cost: $129/year

ProjectionLab is in a different tier than any free tool. It offers:

• Full federal and state tax modeling across all 50 states
• Roth conversion optimization and ladder planning
• ACA subsidy modeling (IRMAA lookback included)
• Social Security optimization
• Multiple income sources, inheritance scenarios, real estate
• Monte Carlo with customizable assumptions

The r/financialindependence community consistently recommends it as the go-to tool for serious FIRE planning once you're within 5–10 years of your number.

Cost-benefit: $129/year is less than 1% of a $20,000 FIRE planning decision. If you're optimizing Roth conversions or ACA subsidy strategies, the tool pays for itself.

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The InvestToFire Calculator Suite

InvestToFire offers a full suite of free calculators beyond the core FIRE tool:

All are free, no signup required.

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How to Use Multiple Calculators Together

The best FIRE planning uses multiple tools as a cross-check:

1. Start with InvestToFire FIRE Calculator — get your baseline FIRE number with pension income factored in
2. Run FIRECalc — test whether that portfolio and withdrawal rate survived all historical periods
3. Run cFIREsim/FIREproof — get a probability estimate using Monte Carlo
4. If your plan has life events or is not in USD — rebuild it in firenum, which models dated events and cash-flow streams month by month across 9 currencies
5. If within 5 years of FIRE — consider ProjectionLab for tax optimization and Roth conversion planning

No single calculator captures everything. Historical testing (FIRECalc) and Monte Carlo (cFIREsim) give you two independent confidence measures, and firenum gives you a third view — the same plan expressed as month-by-month cash flow rather than a single spending number. Use the InvestToFire suite for the specific calculations — Coast FIRE, dividend income, compound interest — that most other tools don't offer.

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Bottom Line

For most FIRE planners, the combination of InvestToFire's free calculator suite (especially the pension-adjusted FIRE number) + FIRECalc (historical testing) + cFIREsim (Monte Carlo) covers 90% of what you need — completely free.

If your plan is more complicated than a flat spending number — a house purchase, a sabbatical, an inheritance — or if you are not planning in dollars, add firenum. It is the only free tool in this list that models the timeline rather than the average.

Add ProjectionLab when you're within 5 years of your FIRE date and optimizing taxes, Roth conversions, and ACA subsidy management matters.

Start with your pension-adjusted FIRE number: FIRE Calculator →