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Compounder

Compound Interest & Retirement Savings Calculator, version 1.0

Compounder is a precise compound interest calculator for iPhone. Project your savings, find the monthly deposit, return or time a goal needs, see how long retirement savings last, and compare two plans. Every number comes from one month-by-month calculation and is checked to the cent.

Download on the App Store Free, with an optional Pro upgrade
Compounder on iPhone showing $691,150.47 after 30 years

Compounder on iPhone

App Store screenshots for iPhone.

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Grow

See exactly how your money grows

Deposits are monthly, so Compounder works through your plan one month at a time and states how it compounds and when you deposit. The parts you see always add up to the total, to the cent.

  • What you put in and what it grew, side by side
  • A growth chart and a year-by-year table
  • Results update as you type
Compounder growth chart showing deposits and growth over 30 years

Goal

Find the deposit that gets you there

Set a target and Compounder solves for the missing piece: the monthly deposit, the annual return, or how long it takes. When a target can't be reached within 100 years, it says so plainly.

Compounder Goal tab showing a monthly deposit of $753.17 to reach $1,000,000 in 30 years

Retire

Know how long your savings last

Start from what Grow projects, choose a monthly withdrawal, and see how many years and months it lasts, or the income your savings can pay for a set number of years.

Compounder Retire tab showing savings that last 34 years 9 months

Everything a savings calculator should show

One exact figure per question, with the assumptions written underneath.

Grow
Final balance, what you put in versus what it grew, a growth chart and a year-by-year breakdown.
Goal
The monthly deposit, the return or the time you need to reach a target. Deposits round up, so you never fall a cent short.
Compare
Two plans side by side: which one ends ahead, and by exactly how much.
Retire
How long your savings last with monthly withdrawals, or the monthly income they can sustain for a set number of years.
Your assumptions, stated
Compounding yearly, half-yearly, quarterly, monthly, daily or continuously, and deposits at the start or end of each month. The result always says which.
Inflation and rising deposits
See results in today's money, and raise your deposit by a percentage every year.
Saved scenarios
Save a plan from any tab and reopen it later, with every input as you left it.
CSV and PDF export
Export the year-by-year table as CSV for free, or a PDF report with the chart.
Your currency, your language
22 currencies and 19 languages, with numbers written the way your region writes them.

One app for iPhone

  • iPhone Built for iPhone, in light and dark, at every text size.

Free to calculate. Pro when you plan further.

Prices are shown in the app and on the App Store in your currency.

Compounder

Free

The core calculators, with no account and no ads.

  • Grow, Goal and Compare
  • Growth chart and year-by-year breakdown
  • CSV export

Compounder Pro

Yearly, monthly or lifetime

All three options unlock the same features, and yearly starts with a 7-day free trial.

  • Retirement planner
  • Inflation-adjusted results
  • Yearly deposit increases
  • Saved scenarios
  • PDF reports

Questions people ask

How accurate is Compounder?

Every number comes from one month-by-month calculation, checked against a high-precision reference. Amounts are rounded once, to the cent, and the parts on screen always add up to the total shown.

Why does my result differ from another calculator?

Usually because of deposit timing or compounding. Compounder deposits monthly, at the end of each month unless you choose the start, and when interest compounds on a different schedule it converts the rate to an exact monthly equivalent. Both assumptions are shown under every result.

Is Compounder free?

Yes. Grow, Goal, Compare, the growth chart, the year-by-year breakdown and CSV export are free. Compounder Pro adds the retirement planner, inflation-adjusted results, yearly deposit increases, saved scenarios and PDF reports, as a yearly subscription with a 7-day free trial, a monthly subscription, or a one-time lifetime purchase.

Where is my data stored?

Only on your iPhone. There is no account, no tracking and no ads, and your plans never leave your device.

Is this financial advice?

No. Compounder is a calculator for estimates before tax, fees and market swings. For decisions about your money, talk to a licensed financial adviser.

Get Compounder

Download on the App Store