Compound Interest Calculator
See what regular saving turns into, broken down year by year.
Reading your result
Fill in every field and the steps will be spelled out here.
How it is calculated
Compounding means your returns start earning returns. With simple interest only the original sum earns; with compounding, last month’s gain works alongside it this month. The gap is barely visible early on and widens sharply later.
That is why time matters more than rate in compounding. The same money at the same rate over 30 years does not produce three times what it produces over 10 — it produces considerably more. Starting early and leaving it alone beats starting late and contributing heavily.
This calculator uses monthly compounding with contributions at the end of each month, which is how most regular savings plans and recurring investments work. Annual compounding produces a slightly smaller figure.
The result is before tax and before inflation. Investment returns are usually taxable, and the rate depends on your country and account type. Separately, at 2% annual inflation, 100,000 in thirty years buys roughly what 55,000 buys today. Treat the number as nominal, not as purchasing power.
Holding the rate constant is itself an assumption. A fixed deposit is certain to maturity; investment returns are not. Even at a 6% average, the path taken changes the outcome. Run an optimistic figure and a conservative one, and plan against both.
Frequently asked questions
How much does compounding actually add?
Very little over short periods, a great deal over long ones. At 6%, 10,000 left for 20 years reaches about 22,000 with simple interest but roughly 33,100 with monthly compounding. Over 30 years the gap widens further.
Is tax included?
No. Tax on interest and dividends varies by country and by account type, and tax-advantaged accounts follow different rules entirely, so there is no single figure to apply. Check what applies where you live.
How do I account for inflation?
Subtract your expected inflation rate from the return before entering it. If you expect 6% growth and 2% inflation, enter 4%. The result then reads in today’s money.
Why is this higher than my savings account?
Many regular savings accounts pay simple interest, and each monthly deposit earns for a different length of time. This calculator assumes returns are reinvested and compound, which produces a larger figure.
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This is a nominal, pre-tax estimate that assumes a constant rate for the whole term. It excludes taxes, fees, inflation and any variation in returns. It does not guarantee the performance of any product and is not investment advice.