Compound interest calculator
See what regular investing turns into: how much you put in and how much interest earns.
Capital growth by year
Table
How compound interest works
Each period, returns accrue on the full balance: the money you put in plus interest already earned. That’s why the curve doesn’t rise in a straight line but gets steeper.
With contributions, the calculator works month by month
- Time matters more than the rate: 10 years instead of 5 gives more than +2% return.
- Regularity beats size: monthly contributions quickly overtake the initial capital.
- Look at the result in today’s money: inflation eats part of it.
How much you need to live on passive income, and how much to save each month to get there — the Wealth Plan financial checkup calculates it.
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How much do you need for passive income?
The financial checkup converts your target income into capital, calculates how much to save and splits your money across three baskets for your risk profile. Free, 10 minutes.
FAQ
What is compound interest?
It’s when returns accrue not only on the money you put in, but also on interest already earned. The longer the term and the more often it compounds, the stronger the effect: after 20–30 years interest can make up most of your capital.
How do I calculate compound interest with monthly contributions?
Each month capital grows by the period’s rate and increases by the contribution. The calculator works month by month, taking your compounding and contribution indexation into account.
What is interest compounding?
It’s adding earned interest to the balance. Monthly compounding gives a slightly better result than quarterly or annual at the same rate.
Why account for inflation?
In 20 years the same amount will buy less. The calculator shows the result in today’s money too, so your goal is honest.
How fast will my capital double?
Roughly in 72 / rate years. At 10% a year — about 7 years. The calculator shows the exact doubling time for your rate.