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Compound interest calculator

See what your money turns into.

Estimate in seconds, then refine in the simulator: contributions, withdrawals and rate changes over up to 100 years.

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Quick estimate

after 20 years

$203,201

Paid in $101,000Returns $102,201
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Latest changes

All changes →
SwitzerlandPillar 3a maximum for 2027 raised to CHF 7,373Contribution limitsItalyTreasury announces a double BTP Valore issue for OctoberProductsAustriaNationalrat passes reform of the second pillar and the AktivpensionRetirementUnited StatesFed raises rates for the first time since 2023MarketGermanyCabinet adopts the Income Tax Reform 2027; flat tax on capital income untouchedTax law

Learning path

All guides →
  1. Compound interest formula explained – with worked examples
  2. Monthly vs. yearly compounding – what the frequency is worth
  3. How much to save per month – a savings plan that holds up
  4. Withdrawal plan – how long a portfolio lasts
  5. Inflation and real returns – what your money will actually buy
  6. The rule of 72 – doubling time in your head
Countries · DE · AT · CH · IT · US · CAInvesting by countryTax rate, allowances, partial exemption and pension facts, each with a source and an as-of date.Open →

How Compound Interest Grows Your Wealth

Compound interest is the foundation of long-term investing. Unlike simple interest, it allows your earnings to generate their own earnings — resulting in exponential growth over time. The earlier and more consistently you invest, the more powerful this effect becomes. This app uses the compound interest formula to simulate how your capital evolves over time by factoring in your contributions, interest rate changes, and withdrawal phases. It recalculates the total balance at each time step by applying the current interest rate to the full amount — including all past interest gains.

Two details decide how the curve looks. The compounding frequency you set for the interest component defines the sub-periods within each year, and contributions and withdrawals are spread across those sub-periods. Where two periods overlap, the one defined last applies — so a contribution and a withdrawal covering the same years do not net against each other.

A = P × (1 + r/n)n × t

  • A = final amount
  • P = initial principal (starting amount)
  • r = annual interest rate (as a decimal)
  • n = number of compounding periods per year
  • t = number of years