MCPCalc

Compound Interest Calculator

Calculate how your savings or investments grow over time with compound interest. See the effect of different compounding frequencies.

Scratchpad (not saved)

$

The starting amount of your investment

$

Amount added each month

%

Annual interest rate (APR)

years

Number of years to grow

How often interest is compounded

What This Calculator Does

Project long-term account growth using compounding, contribution cadence, and time horizon so you can see how deposits and rate assumptions change ending balance.

It combines Initial Investment, Monthly Contribution, Annual Interest Rate, Time Period to estimate Future Value, Total Contributions, Total Interest Earned.

Formula & Method

Core equations: Future value combines lump-sum growth and periodic contributions: FV = P\left(1 + \frac{r}{n}\right)^{nt} + PMT \cdot \frac{\left(1 + \frac{r}{n}\right)^{nt} - 1}{\frac{r}{n}} where P is the initial principal, r is the annual interest rate, n is the compounding frequency per year, t is the number of years, and PMT is the periodic contribution. Inputs are applied in base units, then derived metrics are computed from the same equations and rounded for display.

Notation used in the formulas: R = Future Value; x_{1} = Initial Investment; x_{2} = Monthly Contribution; x_{3} = Annual Interest Rate; x_{4} = Time Period; x_{5} = Compounding Frequency.

Method summary: inputs are normalized to consistent units, core equations are evaluated, then secondary values are derived and rounded for display.

Use this for retirement planning, savings targets, and scenario testing when you need to compare contribution amounts, return rates, and timelines.

Inputs Used

  • Initial Investment: The starting amount of your investment
  • Monthly Contribution: Amount added each month
  • Annual Interest Rate: Annual interest rate (APR)
  • Time Period: Number of years to grow
  • Compounding Frequency: How often interest is compounded

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