Decimal to BCD Converter

How it is calculated

The tool treats the input as a string of decimal digits and encodes each digit on its own as a 4-bit binary number: 0 = 0000, 1 = 0001, up to 9 = 1001. This is 8421 BCD, where the bits of each group are worth 8, 4, 2 and 1. It gives three results: the groups separated by spaces, the same bits joined together as one packed string, and the total bit count, bits = 4 × number of digits. Leading zeros are removed first, so 0007 is read as 7, and the value 0 becomes the single group 0000. Only the digits 0 to 9 are accepted; a minus sign, decimal point, comma, space or letter returns no result. Because each digit takes a full 4 bits, BCD is longer than ordinary binary for the same number.

Common mistakes

• Confusing BCD with the binary form of the whole number. BCD of 47 is 0100 0111, whereas binary 47 is 101111; the two are not interchangeable in a circuit or register.
• Typing a number with a decimal point, thousands separator, space or minus sign, such as 12.5 or 1,234. Each of these returns no result; enter only digits, and handle the sign or fraction separately.
• Expecting leading zeros to be kept. Typing 0007 gives only 0111, so pad the output yourself if a register needs a fixed number of digits.
• Reading the packed string as a binary number. 0010000000100101 is not the binary value of 2025; it only holds the digits 2, 0, 2, 5 in nibbles.
• Assuming every 4-bit group is valid. BCD uses only 0000 to 1001; the patterns 1010 to 1111 never appear in the output and are invalid if you see them in BCD data.