Compound Interest Calculator

Enter a monthly amount, a lump sum, the annual return and years to project the future value.

  • Monthly + lump sum
  • Invested vs gains
  • Nothing you enter is stored

Investment plan

%

Enter the rate and period.

How it works

Enter a monthly investment, an optional lump sum, the expected annual return and the years. Monthly amounts are treated as invested at the start of each month and compounded monthly — the standard SIP projection method.

Future value = monthly × (((1+r)ⁿ − 1) ÷ r) × (1+r) + lump × (1+r)ⁿ

The formula, explained

  • r is the monthly return (annual return ÷ 12), n the total months.
  • Set the monthly amount to 0 to project a lump sum alone.
  • Tax, fees and inflation are not included, so real purchasing power will be lower.

Tips

  • Starting early beats investing more later — compounding accelerates in the back half.
  • Test a lower return too (for example 8% instead of 12%) to see a conservative case.
  • This is a projection, not investment advice or a guaranteed return.

Standards and sources

  • Future value of an annuity-due with monthly compounding (standard finance mathematics)
  • Reference only: markets fluctuate; past performance does not predict future returns

Last reviewed October 7, 2026

Frequently asked questions

How is the future value calculated?

Monthly contributions use the annuity-due formula (invested at the start of each month), compounded monthly. For example, 10,000 a month at 12% for 10 years projects to about 2,323,391.

Is the return guaranteed?

No. The rate you enter is an assumption; real markets rise and fall. Treat the result as a projection, not a promise.

Does it include tax or inflation?

No. Capital gains tax, fees and inflation are not included, so real purchasing power will be lower.

What if I invest only a lump sum?

Leave the monthly amount at 0. A lump sum of 10,000 at 10% for 1 year projects to about 11,047.

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Results are for reference only. Calculations may be wrong and are not legal, medical or financial advice. Always confirm with the relevant authority or a professional before important decisions.