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Compound interest and FIRE calculator.

Move the sliders and watch a portfolio compound year by year, with contributions and interest side by side. Every number updates as you go, the full chart and table sit right below, and any calculation is one link away from a friend.

Want the year you reach FI, and how long the money lasts? That is what the app is for.

Portfolio · 2036Details ›
$0
Passive income $0 /mo
Start
Contributions
Interest
Projection details

Year by year

Year 102036
$0
Portfolio
This yearSo far
Start·
Contributions
Interest

Tap or drag across the chart to pick a year.

YearPortfolioContributionsInterest

Assumptions: annual compounding, deposits at the end of each month, no inflation, passive income at a 4% withdrawal rate. The same defaults as the app.

The app

Three questions. Three calculators. One app.

The calculator above is one of three in simpleFIRE. The app adds the two questions that come next, when you reach your target and how long the money lasts once you live off it, tests every plan against thousands of market scenarios, and then shows every number behind the answer: the chart you tap through year by year, the table, the assumptions.

Projection calculator: result card with portfolio value and passive income, sliders below
What will it grow into?

Projection

Starting portfolio, monthly contribution, period and annual return. Watch the portfolio compound year by year, with your contributions and the interest they earned side by side.

Time to FI calculator: years to target with the FI date and passive income
When do I get there?

Time to FI

Set your FI target and see the year and month you reach it, the passive income it pays, and how far along you are each year. Not sure of your number? The app estimates it from what you spend.

Drawdown calculator: how long the portfolio lasts and when it runs out
How long will it last?

Drawdown

Start taking money out. See the year and month the portfolio runs dry, how much you withdraw along the way, and whether the returns outrun your withdrawals.

Monte Carlo

Plan for the bad years too.

Markets don't pay the same return every year. Switch any of the three calculators to Monte Carlo and your plan is tested against 5,000 market scenarios built on S&P 500 and US Treasury history since 1928. Set your mix of stocks and bonds with one slider, then read the answer at the confidence level you choose, 90% by default: the portfolio you reach, when you reach FI, or the chance your withdrawals last through your planning horizon.

Projection with Monte Carlo: portfolio at the chosen confidence level
Projection details: three confidence levels and a fan of 5,000 scenarios

Projection

The portfolio at your confidence level, two more levels beside it, and a fan of 5,000 scenarios.

Time to FI with Monte Carlo: time to target at the chosen confidence level
Time to FI details: when you reach the target at three confidence levels

Time to FI

When you reach your target at your confidence level, and how that date moves from level to level.

Drawdown with Monte Carlo: chance the portfolio lasts the planning horizon
Drawdown details: chance the money lasts, year by year

Drawdown

The chance your withdrawals last through your planning horizon, year by year up to 100 years.

Method settings: one slider for the mix of S&P 500 stocks and US Treasury bonds

Your mix

One slider for S&P 500 stocks and US Treasury bonds. Return and volatility follow from history.

Everything in the app

Every number, explained.

The result is one tap from the year-by-year story behind it, and every assumption is a slider you can see and change.

Tap through the years

Drag a finger across the chart and the panel follows: contributions and interest for that year and so far.

Today's money or nominal

Inflation is one tap away on every calculator. See every Projection number in what it buys today, or set an FI target that keeps up with prices.

Share it as a PDF or a picture

A clean one-page report with the chart, the assumptions and the yearly table, or an image made for messages and social media.

Saved profiles

Keep several plans, a cautious one and a bold one, and switch between them in a tap.

Your assumptions, your rules

Compounding, contribution timing and yearly increases, withdrawal rate, planning horizon, your stocks and bonds mix: every setting is in plain sight, and every result lists the ones it depends on.

Milestones on the chart

The year interest overtakes your deposits, the month you reach FI, the year the money runs out: flagged where they happen. With Monte Carlo, the chance your money lasts, year by year.

Dark, light, and yours

Two themes, your currency and number format, text that follows your accessibility settings.

iPhone, iPad and Mac

One app across all your Apple devices, with Split View and Slide Over on iPad.

Private by design

No account, no sign-in, no tracking. Your numbers never leave your device. Privacy policy.

Get simpleFIRE for iPhone, iPad and Mac.

Everything on this page, plus Time to FI, Drawdown and Monte Carlo, in your pocket.

Blog

The magic of compounding.

All posts
Ten years of waiting costs $651,000.Same deposits, same return, one decade later. In year 11, your money out-earns you.When interest quietly overtakes your deposits. A million isn't a million.What $1,000,000 buys after thirty years of 3% inflation.
What's new

Version 2.1.0

Full changelog
2.1.0
September 17, 2026

Monte Carlo: plan for the bad years too.

Markets don't pay the same return every year. Switch any calculator to Monte Carlo and test your plan against 5,000 market scenarios built on S&P 500 and US Treasury history. Set your stocks and bonds mix with one slider and choose the confidence level you plan with.

  • Projection: the portfolio you reach at your confidence level, next to two more levels of your choice.
  • Time to FI: when you reach your target at your confidence level.
  • Drawdown: the chance your withdrawals last, year by year up to 100 years.

Also improved

  • Refined presentation of results and charts throughout the app.

Take the calculator with you.

simpleFIRE for iPhone, iPad and Mac. Your numbers stay on your device.