How to use the DEC2BIN() function in Excel

Its converts a decimal number to its binary (base-2) equivalent using two’s complement notation.

Syntax
DEC2BIN(number; [places])

Arguments

• number (required)
  • Decimal integer to convert (range: -512 to +511)
  • Non-integers are truncated (decimal places ignored)
  • Negative values return 10-digit two’s complement binary
• places (optional)
  • Minimum number of binary digits to display
  • Adds leading zeros for positive numbers
  • Has no effect on negative numbers (always 10 digits)
  • Decimal places are truncated if specified

Background
For complete details on two’s complement and number system conversions, refer to the « Number Systems » introduction section.

Examples

=DEC2BIN(1)       // Returns « 1 »

=DEC2BIN(9)      // Returns « 1001 »

=DEC2BIN(10)      // Returns « 00001010 »

Key Features

1. Handles both positive and negative decimal integers
2. Negative numbers always return 10-digit two’s complement results
3. Automatic truncation of fractional values
4. Optional padding for positive numbers only

Common Use Cases

• Digital logic design
• Computer engineering
• Bitmask operations
• Low-level data processing

Error Conditions

• Returns #NUM! if:
  • Number < -512
  • Number > 511
  • Places < required digits for positive numbers
• Returns #VALUE! for non-numeric inputs