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Compound interest calculator

See how your money grows with compound interest and contributions.

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Enter Initial amount, Monthly contribution, Annual rate (%), Duration (years) and the Compound interest calculator works out Final balance, Total invested, Interest earned straight away. For instance, with Initial amount = $10,000.00, Monthly contribution = $200.00, Annual rate (%) = 5 and Duration (years) = 15 it returns Final balance = $74,594.83, Total invested = $46,000.00 and Interest earned = $28,594.83.

How to use it

  1. Enter your values: Initial amount, Monthly contribution, Annual rate (%), Duration (years).
  2. Read the result instantly: Final balance, Total invested, Interest earned.

Frequently asked questions

What does the Compound interest calculator actually compute?

It takes Initial amount, Monthly contribution, Annual rate (%) and Duration (years) and derives Final balance, Total invested and Interest earned from them. The calculation is live as you type, so the result updates on every change.

What information do I need to provide?

4 values: Initial amount ($), Monthly contribution ($), Annual rate (%) and Duration (years). Nothing else is required — no account, no file upload.

Can you show a worked example?

With Initial amount = $10,000.00, Monthly contribution = $200.00, Annual rate (%) = 5 and Duration (years) = 15, the calculator returns Final balance = $74,594.83, Total invested = $46,000.00 and Interest earned = $28,594.83. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

What happens if I enter larger values?

It moves a lot. Using Initial amount = $20,000.00, Monthly contribution = $400.00, Annual rate (%) = 5.5 and Duration (years) = 30 instead, Final balance goes from $74,594.83 to $469,192.51 — which is why it is worth testing a few scenarios rather than trusting a single figure.

What does it give for smaller values?

Scaled down to Initial amount = $5,000.00, Monthly contribution = $100.00, Annual rate (%) = 4.5 and Duration (years) = 8, Final balance comes out at $18,691.55. The relationship is worth checking at both ends before you rely on a single result.

When would I actually use this?

Planning a deposit, a safety net or a large purchase: how much to put aside each month, and how long a target takes at a given rate.

What is the most common mistake?

Reading a nominal rate as if it were real. Inflation is subtracted from the return, not from the capital, so a 3% account during 4% inflation loses purchasing power every year.

What is the difference between the Compound interest calculator and the Compound growth calculator?

This one returns Final balance and Total invested; the Compound growth calculator returns Final value and Total gain. That is the whole difference — open the one whose figure you need.

Is there a tool for the next step?

Simple interest calculator is the closest one after this: Compute simple interest and the final amount from principal, rate and time.

What else is worth having open alongside it?

Interest Rate Calculator and Nominal Interest Rate Calculator — they come up in the same task often enough to be worth a second tab.

Further reading

All guides →
ExplainerHow Does Compound Interest Work?Compound interest is interest earning interest. Here's the formula, a worked example, and why starting early beats saving more later.ExplainerCompounding Frequency, and Where Continuous Compounding Comes From(1 + r/n)^n rises with n but converges on e^r. At 6 percent, monthly and continuous compounding differ by $1.59 on $10,000 over a year. At 24 percent the same gap is $30.07, and over thirty years it is 7.4 percent of the balance.ComparisonSimple vs Compound Interest: What's the Difference?Simple interest grows in a straight line; compound interest snowballs. Here's how each works, a worked example, and which one you meet in real life.ComparisonAPR vs APY: What's the Difference?APR and APY both describe a yearly rate, but only APY includes compounding. Here's what each means and which one actually matters for savings and loans.ExplainerWhat Is a Good Credit Utilization Ratio?Credit utilization is the share of your credit limit you're using. Here's what counts as good, why it matters for your score, and how to lower it.ExplainerThe Rule of 72, ExplainedThe rule of 72 estimates how long money takes to double: divide 72 by the interest rate. Here's why it works, when it's accurate, and how to flip it.