What is Binary-Coded Decimal (BCD)?

BCD is a way of encoding decimal numbers where each individual decimal digit (0-9) is stored as its own 4-bit binary nibble, rather than converting the whole number to pure binary. It's widely used in digital clocks, calculators, and embedded systems where decimal display is more important than compact storage.

How is this different from just converting hex to binary?

A plain hex-to-binary conversion encodes the entire numeric value as one continuous binary number. BCD instead converts the value to decimal first, then encodes each decimal digit separately as its own nibble, which is why the two outputs look different even for the same input, BCD groups its bits by decimal digit, not by the value's raw binary form.

Why does the output length vary?

The output has exactly one 4-bit nibble per decimal digit in the converted value, so a hex input near 15 (one decimal digit) produces 4 bits, while a hex input near 255 (three decimal digits) produces 12 bits.

Can every nibble value from 0000 to 1111 appear in valid BCD?

No, valid BCD nibbles only ever encode the values 0-9 (0000 through 1001); the bit patterns for 10-15 (1010 through 1111) never appear in this tool's output since they don't correspond to a decimal digit.

Does this tool accept a 0x prefix?

Yes, an optional "0x" or "0X" prefix is accepted and stripped before parsing, and hex letters are read case-insensitively either way.

Hex to BCD Converter - Hexadecimal to Binary-Coded Decimal Online

Overview

Introduction

Digital clocks, calculators, and plenty of embedded hardware need to display decimal digits directly, so instead of storing a value as pure binary, they store it as Binary-Coded Decimal: one 4-bit nibble per decimal digit.

This tool takes a hexadecimal value and converts it to that BCD binary string, entirely in your browser.

What Is Hex to BCD Converter?

A converter that reads a hexadecimal value, computes its exact decimal representation, and re-encodes each individual decimal digit as a 4-bit BCD nibble, concatenating the nibbles left to right.

It's the direct inverse of BCD to Hex Converter, and a useful bridge between hex-based tooling and decimal-digit-oriented hardware or display formats.

How Hex to BCD Converter Works

The hex input is parsed (with an optional 0x prefix, case-insensitive digits) into an exact integer using BigInt, then converted to its base-10 string representation with no precision loss even for large values.

Each character of that decimal string is converted individually to a 4-bit binary nibble (0 through 9 map to 0000 through 1001), and the nibbles are joined together in order to form the final BCD binary string.

When To Use Hex to BCD Converter

Use it when you're working with hardware or protocols that expect BCD-encoded values, such as real-time clock chips, seven-segment display drivers, or legacy decimal arithmetic units, and you have a hex source value.

It's also useful for teaching or verifying by hand how BCD differs from a plain binary encoding of the same number.

Often used alongside BCD to Hex Converter and Hex to Decimal Converter.

Features

Advantages

Computes the exact decimal value using BigInt before encoding, so there's no precision loss even for large hex inputs.
Produces a nibble-per-digit output that maps directly onto how BCD hardware and displays actually work.
Runs entirely client-side with no network round trip.

Limitations

Only supports non-negative values; there is no standard BCD convention built in for a sign digit or nibble.
Output length scales with the number of decimal digits in the value, not a fixed bit width, so it won't automatically align to a fixed-width register unless you pad it yourself.

Examples

Converting a two-digit hex value

Input

1F

Output

00110001

Hex 1F is decimal 31; digit 3 becomes 0011 and digit 1 becomes 0001, concatenated as 00110001.

Converting a three-digit decimal result

Input

FF

Output

001001010101

Hex FF is decimal 255; digits 2, 5, 5 become 0010, 0101, 0101, concatenated as 001001010101.

Best Practices & Notes

Best Practices

Remember BCD nibble count tracks the decimal digit count of the value, not the hex digit count of the input, so don't expect a fixed-width relationship between the two.
Use BCD to Hex Converter to reverse the conversion and confirm you recover the original hex value.

Developer Notes

The implementation converts the parsed BigInt value to its decimal string with `.toString(10)`, then maps each character with `Number(digit).toString(2).padStart(4, "0")` before joining, guaranteeing each nibble is always exactly 4 bits regardless of the digit's value.

Hex to BCD Converter Use Cases

Preparing hex-derived values for BCD-based real-time clock chips or seven-segment display drivers
Converting hex test data into BCD for embedded systems or legacy decimal arithmetic hardware
Teaching or demonstrating how BCD encoding differs from plain binary for the same value

Common Mistakes

Expecting BCD output to be the same length as a plain binary conversion of the same value; BCD is almost always longer since it doesn't pack bits as efficiently.
Assuming any 4-bit nibble is valid BCD; only 0000 through 1001 are, the pattern 1010 through 1111 never appears in correct BCD.
Forgetting BCD has no built-in sign convention, so negative hex values aren't supported.

Tips

Pair this with BCD to Hex Converter to round-trip a value and confirm the encoding is correct.
If your target hardware expects a fixed BCD width (like 2 or 4 digits), left-pad the decimal value with zeros before converting so the digit count matches.

Hex to BCD Converter