How to Round Numbers to Three Decimal Places
Decimal places have names associated with their positions. The first decimal place to the right of the decimal point is the tenths place, the second is the hundredths, the third is the thousandths and the fourth to the right is the ten-thousandths place. Rounding is determined by the value of the decimal place to the right of the one you want to round. The number is rounded up, increasing the decimal place's value by 1, if the number to the right is 5, 6, 7, 8 or 9. It is rounded down, keeping the decimal place's value the same, if the number to the right is 0, 1, 2, 3 or 4.
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Instructions
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1
Rewrite any integers and the first two decimal places as given. For example, if you have the number 458.1287, write 458.12.
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2
Look at the values of the third and fourth decimal places. You will use these decimal places to determine the rounded value. In the example, the third decimal place's value is 8 and the fourth decimal place's value is 7.
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3
Round the third decimal place up or down. If the value of the fourth decimal place is 5 or greater, increase the third decimal place's value by 1. If the value of the fourth decimal place is less than 5 (including 0), leave the third decimal place as it is. In the example, since the fourth decimal place is 7, the third decimal place's value will increase by 1 so that it is 9.
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4
Write the rounded third decimal place from Step 3 at the end the number you started in Step 1. Using the example above, 458.1287 rounded to three decimal places is 458.129.
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