Finance Calculator

This calculator projects a single lump-sum deposit forward using annual compound interest, so you can see the future value, how much of it is interest versus your original deposit, and how the numbers shift across different time horizons.

For personal planning only — not financial advice.

Reviewed by CalculatorDrive Finance Editorial Board · Last updated

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Enter amount, annual rate, and time in years to see future value and growth chart.

The short answer

A $10,000 deposit at 5% annual compound interest grows to $16,288.95 after 10 years — $6,288.95 of that is interest, about 38.6% of the final balance. Let it run 20 years and it reaches $26,532.98; 30 years, $43,219.42. The longer the money compounds, the bigger the share that comes from interest rather than your original deposit.

Key takeaways

  • $10,000 at 5% for 10 years grows to $16,288.95 — 38.6% of that final balance is interest.
  • Extending to 20 years reaches $26,532.98, and 30 years reaches $43,219.42 — growth accelerates because each year compounds on a larger base.
  • This tool compounds once a year on a single lump sum, with no added contributions, taxes, or inflation factored in.
  • At 5%, the Rule of 72 estimates the balance doubles roughly every 14.4 years (72 ÷ 5).

The compound interest formula

Future Value = Principal × (1 + rate)^years

= $10,000 × (1.05)^10 = $16,288.95

Because each year's interest gets added to the balance before the next year's interest is calculated, the growth curve isn't a straight line — it bends upward. Total interest earned is simply the future value minus the original principal: $16,288.95 − $10,000 = $6,288.95.

Why time matters more than the rate

Holding the rate fixed at 5% and only changing the number of years shows how much of the heavy lifting comes from time rather than the rate itself:

10 years: $16,288.95 ($6,288.95 interest)

20 years: $26,532.98 ($16,532.98 interest)

30 years: $43,219.42 ($33,219.42 interest)

Interest earned in the second decade ($10,244.03) is larger than interest earned in the first ($6,288.95), and interest in the third decade ($16,686.44) is larger still — the same $10,000 deposit, the same 5% rate, purely more time to compound. That's the core argument for starting early rather than waiting for a higher rate.

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Frequently Asked Questions

What is compound interest and why does it matter?

Compound interest reinvests earned interest back into your balance, so future interest is calculated on a growing base. A $10,000 deposit at 5% grows to $16,288.95 after 10 years, and $6,288.95 of that — 38.6% of the final balance — is interest, not the original deposit.

How does time affect investment growth?

The longer your money compounds, the more each year contributes to total growth. That same $10,000 at 5% reaches $26,532.98 after 20 years and $43,219.42 after 30 years — the second decade adds more than the first, and the third adds more than the second, purely from compounding.

What is future value?

Future value is the total amount you will have at the end of an investment period, including both your original deposit and all compounded interest. It answers how much today's money could be worth at a fixed rate over time.

Are these results guaranteed?

No. This calculator assumes a fixed annual return with no withdrawals, taxes, or inflation, and compounds once per year with no added contributions. Real investments fluctuate, and inflation reduces purchasing power even when your balance grows.

How much of my future balance is interest versus principal?

At higher rates or longer periods, interest makes up a larger share of the total. On $10,000 at 5% for 10 years, interest is 38.6% of the ending balance; stretch that to 30 years and interest grows to over three times the original deposit.

How do I use this finance calculator?

Enter your principal, annual interest rate, and number of years, then click Calculate. You will see future value, total interest, a growth chart, and a comparison across different time horizons.

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