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Kordu Tools
Finance Runs in browser Updated 30 Mar 2026

Compound Interest Calculator

Project how your savings grow over time with compound interest, monthly contributions, and different compounding frequencies.

Investment details

Future value£302,370.09
Total contributions£130,000.00
Total interest earned£172,370.09

Growth over time

Contributions
Interest earned

Year-by-year breakdown

YearStart balanceContributionsInterestEnd balance
110,000.006,000.00955.3416,955.34
216,955.346,000.001,458.1424,413.48
324,413.486,000.001,997.2932,410.77
432,410.776,000.002,575.4140,986.18
540,986.186,000.003,195.3350,181.52
650,181.526,000.003,860.0660,041.58
760,041.586,000.004,572.8570,614.43
870,614.436,000.005,337.1681,951.59
981,951.596,000.006,156.7294,108.31
1094,108.316,000.007,035.54107,143.85
11107,143.856,000.007,977.88121,121.72
12121,121.726,000.008,988.34136,110.06
13136,110.066,000.0010,071.84152,181.91
14152,181.916,000.0011,233.68169,415.59
15169,415.596,000.0012,479.50187,895.09
16187,895.096,000.0013,815.39207,710.48
17207,710.486,000.0015,247.84228,958.32
18228,958.326,000.0016,783.85251,742.18
19251,742.186,000.0018,430.90276,173.08
20276,173.086,000.0020,197.01302,370.09
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How to use Compound Interest Calculator

  1. Enter your principal

    Type the amount you are starting with — your initial savings or lump-sum investment.

  2. Set monthly contributions

    Add a regular monthly contribution amount if you plan to deposit money each month. Set to zero for a one-time investment.

  3. Enter the interest rate and term

    Type the annual interest rate and the number of years you want to project.

  4. Choose compounding frequency

    Select daily, monthly, quarterly, or annually to see how compounding frequency affects your returns.

  5. Review the results

    See your projected future value, total contributions, and total interest earned at a glance.

  6. Explore the year-by-year breakdown

    Scroll through the table and growth chart to see exactly how your money compounds each year.

Compound Interest Calculator FAQ

What is the compound interest formula?
A = P(1 + r/n)^(nt), where A is the future value, P is the principal, r is the annual interest rate as a decimal, n is the number of compounding periods per year, and t is the time in years. This calculator adds monthly contributions on top of this formula.

What is compound interest?
Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods. It causes money to grow faster than simple interest because you earn interest on your interest.

How does compounding frequency affect returns?
More frequent compounding produces slightly higher returns because interest is added to the principal sooner. Daily compounding earns marginally more than monthly, which earns more than annual. The difference is small but grows over long time periods.

Is this adjusted for inflation?
No. The calculator shows nominal growth. To approximate real (inflation-adjusted) returns, subtract the expected annual inflation rate from the interest rate you enter. For example, if the rate is 7% and inflation is 3%, use 4%.

Can I use this for ISAs or index funds?
Yes. Enter your current balance as the principal, your monthly contribution, and the expected annual return rate. The result shows projected growth assuming a constant rate — actual investment returns vary.

What is the difference between APR and AER?
APR (Annual Percentage Rate) is the nominal rate without compounding. AER (Annual Equivalent Rate) reflects the true annual return after compounding. If your savings account quotes AER, use that rate with annual compounding to get accurate results.

How accurate are the projections?
Projections assume a constant interest rate and consistent monthly contributions. Real savings accounts, ISAs, and investments have variable rates. Use the results as a planning estimate, not a guaranteed outcome.

What does the growth chart show?
The chart shows your cumulative contributions as one area and the interest earned on top as a second area. The gap between them widens over time, illustrating how compound growth accelerates.

Is my data sent anywhere?
No. All compound interest calculations happen entirely in your browser. Nothing is uploaded, stored, or logged.

Background

Enter an initial investment, monthly contribution, annual interest rate, and time period to see your projected future value. Uses the standard compound interest formula A = P(1 + r/n)^(nt) with contributions added each period. Choose from daily, monthly, quarterly, or annual compounding to see how frequency affects your final balance. Results show total contributions, total interest earned, and the final balance. A visual growth chart illustrates how contributions and interest stack up over time, and a year-by-year breakdown table details every year's opening balance, contributions, interest earned, and closing balance. Useful for modelling savings accounts, ISAs, index fund growth, and retirement planning. All calculations run in your browser — nothing is sent to any server.

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