Estimated Future Value
$ {{ format(endingBalance) }}
$ {{ format(totalPrincipal) }} Principal $ {{ format(totalInterest) }} Interest {{ ((totalPrincipal/endingBalance)*100).toFixed(0) }} % P / {{ ((totalInterest /endingBalance)*100).toFixed(0) }} % I
$
% / yr
yrs mos
$
$
%
%
Year Deposit ($) Interest ($) Ending ($)
{{ r.year }} {{ format(r.depositCum) }} {{ format(r.interestCum) }} {{ format(r.ending) }}
Month Deposit ($) Interest ($) Ending ($)
{{ r.period }} {{ format(r.depositCum) }} {{ format(r.interestCum) }} {{ format(r.ending) }}
Categories: Finance
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Compound interest refers to growth where interest is added to the principal so that future interest is calculated on the increased total. Unlike simple interest, the compounding process accelerates savings growth over time. Understanding its mechanics helps you evaluate investment products, retirement plans, and any scenario where returns are periodically reinvested.

The Compound Interest Calculator lets you input principal, contributions, interest rate, compound frequency, tax and inflation to model real-world investment scenarios. It instantly produces annual and monthly schedules, summary figures, and interactive charts. The tool's clear outputs clarify how each factor influences growth, helping you test alternative strategies with minimal effort.

You will gain actionable insight by comparing scenarios such as higher monthly deposits, more frequent compounding, or deferred contributions. The schedules reveal when contributions overtake earnings, while breakdown charts highlight the share of principal versus interest. Use these findings to refine saving goals, inform discussions with financial advisers, and monitor progress toward long-term targets.

Technical Details:

The calculator performs real-time projections using deterministic formulas and client-side rendering.

  • Separate inputs for initial investment, annual and monthly contributions.
  • Selectable compounding: annual, semi-annual, quarterly or monthly.
  • Option to add contributions at the beginning or end of each period.
  • Tax and inflation fields adjust nominal returns to real values.
  • Annual and monthly schedules summarise deposits, interest and ending balance.
  • Interactive donut and stacked-bar charts clarify balance composition.
  • URL parameters let you share or bookmark configured scenarios instantly.
Core Formulas
Compound growth A = P (1 + r/n) ^ (n · t)
Contribution series A_c = C · ((1 + r/n) ^ (n · t) – 1) / (r/n)
Total balance A_total = A + A_c

Calculations-and-Scoring:

This section explains how the tool derives each result and how to interpret the figures.

Formula Breakdown

The calculator splits growth into principal, contributions and interest. Interest is compounded every selected period after tax. Inflation reduces the real value to express purchasing power.

Worked Example

Suppose you invest $20 000, add $5 000 yearly, earn 5 % interest compounded annually for 5 years, pay 0 % tax and expect 3 % inflation. The nominal ending balance is $53 152, where 47 % is principal and 53 % is interest.

Interpretation

Compare the interest share across scenarios. A rising percentage suggests compounding drives growth more than new contributions.

Recommendations

Increase contribution size or frequency to boost principal early. Reinvest interest whenever possible. Review inflation assumptions yearly.

Step-by-Step Guide:

Follow these steps to model your investment scenario.

  1. Enter the Initial investment amount.Tip
  2. Set the Interest rate and choose the Compound frequency.
  3. In Length, provide years and months to match your horizon.
  4. Click Advanced, then add annual or monthly contributions as needed.
  5. Adjust Tax rate and Inflation rate to reflect your environment.Caution
  6. Close the panel; results, tables and charts refresh instantly below.

FAQ:

Find quick answers to common questions.

Does the calculator handle irregular deposits?

The model assumes regular monthly and annual contributions. For irregular amounts, average them or run separate scenarios.

Can I simulate withdrawals?

Withdrawals are not currently supported. Treat negative contributions as a workaround, or export the schedule and adjust externally.

Why is the real balance lower than the nominal?

Real values discount the effect of inflation, showing what the balance could buy in today’s money.

How precise are the projections?

The calculator uses deterministic formulas without market variability. Actual investment returns may differ.

Do you store any personal data?

No. All calculations run in your browser. Parameters persist only in the shared URL, which you control.

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