How Can I Truncate a Decimal Value Without Rounding Up?

Precise Decimal Truncation: Avoiding Rounding Up

This guide demonstrates how to truncate a decimal number (e.g., 3.4679 to 3.46) without the inaccuracies of standard rounding functions. Methods like Math.Round() can be unreliable for pure truncation.

The Truncation Method

The solution employs a simple yet effective technique:

value = Math.Truncate(100 * value) / 100;

This works in three steps:

1. Shift the Decimal: Multiply the value by 100 (or 10ⁿ for n decimal places). This moves the decimal point two places to the right.
2. Truncate the Integer: Use Math.Truncate() to remove the fractional part, leaving only the integer portion.
3. Restore the Decimal: Divide the result by 100 (or 10ⁿ), shifting the decimal point back to its original position.

Important Considerations

It's crucial to understand that floating-point arithmetic can introduce minor inaccuracies. This is inherent in how computers represent decimal numbers. For applications demanding absolute precision, consider using decimal data types or implementing custom rounding logic tailored to your specific needs.

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