How to Calculate Investment Return and Compare Risk

A dollar gain and a percentage return answer different questions. If two investments each gained $100 but one required $1,000 and the other $10,000, their returns were not equal. FINRA defines rate of return as total return divided by the amount invested. That calculation is useful only when the cash flows, costs, and time periods are comparable.

Calculate a simple holding-period return

Start with the ending value, add any cash income received, subtract the starting value and direct transaction costs, then divide by the starting value. Suppose you buy an investment for $1,000, receive $30 in income, and sell it for $1,070 after paying $10 in transaction costs. The net gain is $90 ($1,070 + $30 − $1,000 − $10), or 9% of the $1,000 starting amount. If the ending value plus income minus costs were only $900, the result would be a 10% loss. This simple formula assumes one initial contribution and no later deposits or withdrawals.

Check the time period and hidden costs

A 9% gain over one year is different from 9% over five years. An annualized figure expresses a multi-year return as an equivalent yearly rate; it is not the same as dividing the total percentage by the number of years when returns compound. FINRA explains why holding period and annualization matter. Account fees, fund expenses, trading costs, and taxes can reduce what you keep. The SEC shows how ongoing fees affect portfolio value.

Return is not a measure of safety

Two investments with the same past return may expose you to different chances of loss, different access to your money, and different inflation risk. The SEC describes market, liquidity, inflation, and other investment risks. A high projected return is not compensation for a risk you have not understood. Compare a result with an appropriate benchmark over the same period and ask whether the investment fits when you need the money. Our beginner investing guide covers diversification and fees.