How Can I Truncate, Not Round, Decimal Values to a Specific Number of Places?

Truncate the number of decimal places accurately to avoid rounding

When processing numerical values, we sometimes need to truncate decimals to a specified number of digits to avoid errors caused by rounding. This is not an easy task, as the example in the article shows, truncating 3.4679 to two decimal places, many methods will get the result of 3.47.

A reliable method is to use mathematical truncation, which simply removes all numbers after the specified precision. This can be achieved using the following formula:

<code>value = Math.Truncate(100 * value) / 100;</code>

The formula first multiplies the value by 100 and moves the decimal point two places to the right. Then, use the Truncate function to truncate the decimal part, removing all digits after the decimal point. Finally, divide the result by 100 to return to the original number of decimal places.

Using this formula, 3.4679 can be truncated to 3.46:

<code>value = Math.Truncate(100 * 3.4679) / 100;</code>

It should be noted that due to limitations of computer arithmetic, fractions represented by floating point numbers, such as 0.1 or 0.2, may not be completely accurate. Therefore, potential differences in accuracy need to be treated with caution when working with such values.

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