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Compound Interest Calculator

Estimate savings growth with an initial deposit, monthly contributions and monthly or yearly interest. Compare total invested, earned interest and final balance.

Investment details

Growth summary

Final balance
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Total invested
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Total interest earned
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Assumes a constant rate, monthly compounding and deposits at the end of each month. Annual rates are effective: 12% yearly is about 0.9489% monthly. Amounts share your chosen currency; no exchange, fees, taxes or inflation are included. Estimates are not guaranteed returns.

Compound Interest Explained: A Beginner’s Guide to Growing Savings

Compound interest means earning interest on both your original money and interest already earned. Regular deposits and time can help savings grow, but real investments may fluctuate or lose value. Use this estimate to compare possibilities, not to predict a guaranteed outcome.

How interest on interest works

  1. Start with your deposit. With 1,000 at an effective 12% annual rate and no additional deposits, the balance becomes 1,120 after one year.
  2. Let earnings grow too. In year two, the same 12% applies to 1,120, earning 134.40. Your balance becomes 1,254.40: 254.40 of interest on 1,000 invested.
  3. Add regular savings. With 1,000 initially, 100 added at each month-end and 1% monthly interest for two months, you invest 1,200 and earn 21.10, giving a final balance of 1,221.10.

Build a simple savings plan

  1. Choose realistic inputs. Enter your starting money and an affordable monthly contribution. Use zero if you do not plan additional deposits. Match the rate toggle to the quoted monthly or effective yearly rate.
  2. Compare time and contributions. Select whole years or months and compare a shorter plan with a longer one. Increasing deposits adds your own money; interest is the extra growth above those deposits.
  3. Understand the formula. For n months and monthly rate r, balance = P × (1 + r)^n + C × ((1 + r)^n − 1) ÷ r. P is the initial deposit and C the month-end contribution. At 0%, balance = P + C × n. Effective annual rates convert using r = (1 + annual rate ÷ 100)^(1/12) − 1. Only displayed totals are rounded.

Frequently Asked Questions

What is the difference between simple and compound interest?

Simple interest applies only to the original deposit. Compound interest also applies to previously earned interest, so growth can accelerate over time.

Is 12% yearly the same as 1% monthly?

No. This calculator uses effective annual rates. A 1% monthly rate compounds to about 12.6825% per year; 12% effective yearly converts to about 0.9489% monthly.

When are monthly contributions added?

At the end of each month, after that month’s interest. A deposit begins earning interest in the following month. Beginning-of-month deposits would produce a different result.

Can I use a zero interest rate?

Yes. The final balance then equals the initial deposit plus all monthly contributions, and total interest is zero.

Does this include taxes, fees or inflation?

No. These estimates are before costs and do not adjust purchasing power. Real returns vary; compare provider terms and use qualified advice for personal financial decisions.

How much should I save each month?

Choose an amount that fits your budget while keeping money available for essential expenses and emergencies. Test different contributions and durations; the calculator does not recommend a specific investment.

Are my financial inputs saved?

No. These calculations run in your browser without storing or sending your entered amounts. Copying results places the summary on your device’s clipboard.

Important Financial & Investment Disclaimer

The calculations and growth summaries provided by this tool are purely mathematical simulations based on a constant rate and are intended solely for general educational and informational purposes. They do not represent guaranteed financial returns, historical investment performance, or official bank projections.

This website does not provide investment advice, financial planning, or wealth management services. Real-world financial products are subject to market volatility, management fees, transaction costs, inflation, and local taxation, none of which are accounted for in these estimates. Always consult a certified financial planner, accountant, or licensed investment advisor before making any real-world financial commitments or investment decisions.