The FIRE calculator app for iPhone

By Kevin Lan · Updated October 2026

A FIRE calculator app estimates your FIRE number (the amount you need invested to live off your portfolio) and projects the year you'll reach it, then keeps that date in view on your phone. Here's what separates a genuinely useful one from a countdown toy.

What FIRE: Retirement Calculator includes

Here is what this app includes, so you can weigh it against the criteria below.

• Computes your FIRE number and the year you reach it from your own inputs (age, current investments, contributions, retirement spending, and expected return), and shows the formula worked through with your figures. Enter contributions, spending, and part-time income per month or per year, whichever you know.
• Plans in real, after-inflation dollars, with an adjustable safe withdrawal rate (a 2% to 7% slider, or type a rate from 0.5% to 20%).
• A home-screen and lock-screen countdown widget that counts down to your computed date and moves as your net worth grows.
• Milestone reminders and a monthly check-in, free: a note for each year to go, the final days, and when your plan projects 25%, 50%, and 75% of your FIRE number, plus a reminder on the 1st to update your investments. Both are scheduled on your phone.
• Six FIRE variants (Pro): Traditional, Coast, Barista, Lean, Chubby, and Fat, each from your own numbers.
• Monte Carlo simulation (Pro) across 2,000 market paths that estimates the chance your money lasts, plus side-by-side what-if scenarios.
• Social Security and pension income (Pro), phased in by age.
• Account for taxes (Pro): treat your spending as after-tax and add the taxes you will owe on withdrawals, so your number and date reflect what you will really need.
• Works offline, with no account and no analytics. Optional sync goes through your own private iCloud, and an optional Face ID or Touch ID lock keeps the app private. The App Store privacy label is Data Not Collected.
• Free to find your FIRE number and countdown. Pro is a one-time $19.99 unlock, not a subscription.

Finding your FIRE number, the countdown, and the widget are free. The deeper tools (FIRE variants, Monte Carlo, scenario comparison, Social Security and pension, and taxes) are the optional one-time Pro unlock, and every install starts with 14 days of Pro free.

What a good FIRE calculator app does

• It computes your number from your own inputs. A useful app takes your age, investments, contributions, expenses, and expected return and returns your FIRE number and the year you reach it, not a generic chart.
• It uses real, after-inflation returns. Planning in today's dollars keeps a figure decades out meaningful. An app that only uses a nominal return overstates what your money will buy.
• It covers the FIRE variant you care about. Coast, Barista, Lean, Chubby, and Fat FIRE each change the target. The math is the same; the app should let you pick.
• It shows the math. You should be able to see the formula worked through with your numbers, not just a result you have to trust.
• It keeps the date in front of you. A home-screen widget that counts down to your computed date, and updates as your net worth grows, is what turns a one-time calculation into something you use.
• It respects your privacy. Financial inputs are sensitive. Look for on-device storage, no account, no analytics, and a clear App Store privacy label.
• It doesn't lock the basics behind a subscription. This category resents subscriptions on what reads as a calculator. Free-to-calculate with an optional one-time upgrade is the friendlier model.

How a FIRE calculator works

Every FIRE calculator rests on two steps. First it finds your FIRE number: your annual retirement spending divided by a safe withdrawal rate, so a 4% rate works out to 25 times your yearly spending. Then it projects how your investments grow from where they stand today, adding your yearly contributions and compounding at your expected return, until the balance reaches that number. The year that happens is your financial-independence year.

The details are where calculators differ. Planning in real, after-inflation dollars keeps a figure decades out meaningful. Accounting for the taxes you will owe on withdrawals changes the target. Letting you set the withdrawal rate matters too, because 3% and 5% produce very different numbers. This app shows the formula worked through with your own figures, so the result is something you can check rather than take on faith.

Web calculator or app: which do you need?

For a one-time answer, a web calculator like the one below is enough. It finds your number and date in seconds with nothing to install. An app earns its place when you want that date to stay in view and move as your net worth changes, or when you want deeper tools: a Monte Carlo success check, side-by-side scenarios, or Social Security and pension planning. Not everyone needs the app; the ones who do tend to be the ones who want to watch the number every week.

References

• Investopedia. Financial Independence, Retire Early (FIRE): a definition. investopedia.com
• Bengen WP. Determining withdrawal rates using historical data. Journal of Financial Planning. 1994;7(4):171–180. The paper that introduced the 4% withdrawal guideline.
• Damodaran A. Historical annual returns on U.S. stocks, bonds and bills (1928–present). NYU Stern School of Business. pages.stern.nyu.edu/~adamodar

Frequently asked questions

Related

Put your plan on your home screen. FIRE: Retirement Calculator finds your FIRE number free and counts down to your financial-independence date on your iPhone. No account, no subscription. Download on the App Store.

On a computer? Scan with your iPhone camera to get the app.