Return on investment is a measure of investment performance used by both professional and novice investors alike. By dividing the loss or gain on the investment from one day by the original cost of the investment (day 1 market value), potential investors can compare investment opportunities by looking at the daily return percentage rate.

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Determine the original value of the asset; that is, the value of the asset on Day 1. For instance, if you purchased a money market account for $10,000 on Day 1, the value of the asset on Day 1 is $10,000.

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Determine the value of the asset on Day 2. Let's say your money market account grew to $10,050 in one day.

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Take the difference between Day 1 and Day 2. The difference is $10,050 - $10,000 or $50.

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Divide the difference by Day 1 for the ROI. The answer is $50 / $10,000 or 0.005.

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Multiply by 100 for a daily percentage rate of return. The answer is 0.005 x 100 = 0.5 percent.