Investment Calculator

Use this Investment Calculator to estimate how an initial investment and regular contributions may grow over time. It can also estimate total contributions, investment growth, inflation-adjusted value, and the difference between your projection and an optional target.

Important: Investment projections are estimates, not guaranteed returns. Actual results can be higher or lower because of market performance, fees, taxes, inflation, and other factors.

Investment Calculation Method

The calculator converts the expected annual return to a monthly rate:

Monthly rate = annual return ÷ 12 ÷ 100

Growth of the initial investment:

FV of initial investment = initial investment × (1 + r)ⁿ

Growth of regular monthly contributions:

FV of contributions = contribution × [((1 + r)ⁿ − 1) ÷ r]

Then:

Future investment value = FV of initial investment + FV of contributions

Where r is the monthly return rate and n is the number of months.

If yearly contributions are selected, the calculator converts them to a monthly equivalent for the projection.

Total Contributions and Growth

Total contributions = initial investment + regular contributions made during the term

Investment growth = future value − total contributions

Inflation-Adjusted Value

If an inflation rate is entered:

Inflation-adjusted value = future value ÷ (1 + inflation rate)^years

This gives an approximate estimate of the future balance in today’s purchasing power.

Target Gap or Surplus

If a target future value is entered:

Gap or surplus = projected future value − target value

A positive result means the projection is above the target; a negative result means it is below the target.

Example

Suppose you start with $5,000, contribute $300 per month for 10 years, and assume a 6% annual return.

Monthly rate = 6% ÷ 12 = 0.5%

Total contributions = $5,000 + ($300 × 120) = $41,000

Using monthly compounding:

Projected future value ≈ $58,260.79

Estimated investment growth ≈ $58,260.79 − $41,000 = $17,260.79

If inflation averages 3% per year, the projected balance has an estimated present purchasing-power value of approximately $43,351.50.

Important Notes

• The expected return is an assumption and should not be treated as a guaranteed annual return.
• Real investments normally experience gains and losses rather than the same return every month.
• The calculation assumes regular contributions and simplified monthly compounding.
• Investment fees, fund expenses, advisory charges, transaction costs, and taxes are not automatically deducted.
• Even relatively small ongoing fees can significantly reduce long-term investment value.
• Inflation can vary substantially over time, so the inflation-adjusted result is only an estimate.
• The calculator does not account for withdrawals, changing contribution amounts, changing return rates, dividends taxed separately, or investment-specific risks.
• A projected target surplus does not mean an investment strategy is suitable or sufficiently diversified.

Consider testing several return, contribution, inflation, and investment-term assumptions instead of relying on a single projection.

Sources

• Investor.gov — Compound Interest Calculator
• Investor.gov — Savings Goal Calculator
• U.S. Securities and Exchange Commission — How Fees and Expenses Affect Your Investment Portfolio