I Want To Retire Today vs FireCalc: Which FIRE Calculator Is Better?
FireCalc has been the go-to retirement calculator for DIY investors since the early 2000s. It pulls every rolling historical period from 1871 to the present and shows you how often your plan would have survived. It's thorough, well-respected, and completely free. If you've spent time on Bogleheads or r/financialindependence, you've probably used it.
I Want To Retire Today takes a different approach. Instead of replaying history, it runs 1,000 Monte Carlo simulations to model a range of possible futures. You enter 5 inputs, get a retirement date in seconds, and see exactly which levers move that date fastest. It's built for speed, mobile, and sharing — designed for people who want a quick, actionable answer without navigating tabs and sub-menus.
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Enter your savings, income, contributions, expenses, and age. Get your retirement date instantly with Monte Carlo simulation.
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Side-by-side breakdown of what each calculator offers.
| Feature | I Want To Retire Today | FireCalc |
|---|---|---|
| Inputs needed | 5 | 3 basic + tabs |
| Time to result | 5 seconds | 2–5 minutes |
| Simulation | Monte Carlo (1,000 runs) | Historical backtest (1871–present) |
| Social Security | One-tap chip | Separate tab |
| Tax support | Filing status + effective rate | None |
| Sensitivity analysis | Auto "Retire faster" ranking | None |
| UI / Mobile | Modern, mobile-optimized | 2000s-era desktop |
| Sharing | OG image + URL + share card | None |
| Price | Free | Free |
When to use I Want To Retire Today
Quick FIRE date check
You want to know when you can retire, not spend 20 minutes configuring tabs. Enter 5 numbers, get a date. Done.
Mobile-first planning
FireCalc was built for desktop browsers in the early 2000s. If you're checking your retirement plan on your phone — at lunch, on the train, wherever — our interface was designed for that.
Sharing results
Want to share your retirement plan with your spouse, a financial advisor, or a Reddit thread? I Want To Retire Today generates a shareable URL with an OG image card. FireCalc has no sharing functionality.
Sensitivity analysis
The “Retire faster” section automatically ranks which changes to your plan — saving more, spending less, adding Social Security — have the biggest impact. FireCalc leaves this analysis entirely to you.
When to use FireCalc
Historical backtesting purist
If you want to know exactly how your plan would have performed in every 30-year period since 1871, FireCalc is the gold standard. Its historical backtest is comprehensive and well-validated. Some planners prefer real data over simulated scenarios, and that's a legitimate preference.
Testing alternative withdrawal strategies
FireCalc supports withdrawal methods like Bernicke (decreasing spending in retirement), percentage of remaining portfolio, and fixed-dollar approaches. If you're modeling a specific withdrawal strategy beyond the standard 4% rule, FireCalc gives you more knobs to turn.
The Social Security factor
Social Security is the single biggest variable most retirement calculators ignore or make hard to use. For someone earning $80,000/year, estimated Social Security benefits are roughly $2,200–$2,500/month. That's $26,400–$30,000/year in guaranteed income that reduces how much your portfolio needs to cover.
The impact is dramatic. If your annual expenses are $60,000 and Social Security covers $28,000, your portfolio only needs to generate $32,000/year. At a 4% withdrawal rate, that's $800,000 instead of $1,500,000 — nearly half the savings required.
FireCalc lets you enter Social Security income, but you have to navigate to the “Other Income/Spending” tab and manually input the amount and start age. I Want To Retire Today offers a one-tap Social Security chip that estimates your benefit based on your current income. One tap vs. a research project — that UX difference matters when you're trying to quickly model different scenarios.
Frequently asked questions
Is FireCalc more accurate than I Want To Retire Today?
Not necessarily. FireCalc uses historical backtesting — it replays every rolling period from 1871 to the present and shows what percentage survived. I Want To Retire Today uses Monte Carlo simulation with 1,000 randomized runs. Both are valid approaches. Historical backtesting tells you what happened; Monte Carlo tells you what could happen across a wider range of scenarios. Neither predicts the future. The real question is which output format helps you make better decisions.
Does FireCalc have Monte Carlo simulation?
FireCalc offers a 'random performance' option in its 'Your Portfolio' tab, but it's not the default and requires navigating to find it. The core experience is historical backtesting. I Want To Retire Today runs Monte Carlo as the default simulation engine — 1,000 randomized runs every time, with no extra setup.
Which calculator is better for early retirement (FIRE)?
For a quick FIRE date check — when can I retire given my current savings, contributions, and spending — I Want To Retire Today is faster and more visual. You get a date, a success rate, and sensitivity analysis in seconds. FireCalc is better if you want to stress-test a specific withdrawal plan against every historical cycle going back to 1871. For most FIRE planners, starting with I Want To Retire Today and then sanity-checking with FireCalc is a solid approach.
Can I use both calculators together?
Absolutely, and many serious FIRE planners do. Use I Want To Retire Today for the initial reality check — enter your 5 inputs, get a retirement date, see what levers move it fastest. Then use FireCalc to stress-test that plan against historical cycles if you want extra confidence. The tools complement each other well because they use different simulation methods.
Why doesn't FireCalc support Social Security input easily?
FireCalc does support Social Security, but it's in a separate tab called 'Other Income/Spending' where you manually enter the amount and start year. I Want To Retire Today offers a one-tap Social Security chip that auto-calculates your estimated benefit based on your income. The difference is UX — FireCalc gives you the option, but makes you do the research. Our tool estimates it for you.
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