BCD to Hex Converter
Convert a BCD (binary-coded decimal) value into hexadecimal — unpack each decimal digit and re-encode the number in true hex.
Built by
Swapnil SanghviFull-Stack Web Developer & WordPress Developer
Swapnil Sanghvi is a full-stack web and WordPress developer, UI designer, and full-time freelancer who builds and maintains Hex Calculator.
Further reading: Character encoding — Wikipedia
How to Convert BCD to Hex
Each decimal digit of a BCD value becomes its own hex nibble directly — no base-16 positional math involved. 59 in packed BCD becomes the hex digits 5 and 9, written as 0x59, not the hex result of an ordinary decimal-to-hex conversion (which would be 0x3B).
BCD to Hex Example, Step by Step
59 (BCD) = 0x59
59 in packed BCD = 0x59
Decimal digits: 5 9 Hex nibbles: 5 9 Write directly as hex: 0x59
| Step | Description | Result |
|---|---|---|
| Read the decimal digits | 5, 9 | 2 digits |
| Write each digit as its own hex nibble | 5 -> 0x5, 9 -> 0x9 | 0x59 |
This is not the same as an ordinary decimal-to-hex conversion — 59 as a plain decimal number converts to 0x3B, not 0x59. Packed BCD keeps each digit in its own nibble instead of doing base-16 math.
Where BCD to Hex Actually Comes Up
Reading a Real-Time Clock Chip
RTC chips like the DS3231 report hours, minutes, and seconds packed as BCD nibbles — converting that raw register value to its hex representation is the first step before using it anywhere else in code.
BCD 59 (seconds) -> 0x59
Decoding a Seven-Segment Display Driver
Digital displays that drive their segments from BCD input store the digit they're showing in BCD — converting to hex helps when logging or debugging what a display controller is actually holding.
BCD 7 -> 0x07
Working With Legacy Financial Data
Older mainframe and COBOL systems represent exact decimal currency values in packed BCD to avoid floating-point rounding — converting to hex is often a step in migrating that data to modern formats.
BCD 9999 -> 0x9999
Common Mistakes When Converting BCD to Hex
- Entering A-F as if they were valid BCD digits — BCD only uses 0-9.
- Doing an ordinary decimal-to-hex conversion instead — 59 as a plain decimal number converts to 0x3B, but 59 in packed BCD is 0x59. The two operations aren't interchangeable even though they take the same-looking input.
- Forgetting leading zero nibbles are still significant digits in BCD.
Why Use This Calculator Instead of Doing It by Hand
- Validates that every nibble is a real BCD digit (0-9) before converting
- Handles values of any length with arbitrary-precision arithmetic
- Runs entirely in your browser — nothing you type gets sent anywhere
- Shows decimal and binary for the same value alongside the hex result
Limitations
- Accepts decimal digits (0-9) only, one digit per position — if you're working with strict packed-BCD hardware encoding, verify a known test value against your own reference first.
Frequently Asked Questions
How do you convert BCD to hex?
Each decimal digit becomes its own hex nibble directly — 59 in packed BCD becomes 0x59, not 0x3B (which is what a normal decimal-to-hex conversion of 59 would give). There's no base-16 math involved.
Why doesn't the BCD input accept letters A-F?
Because a valid BCD nibble only ever represents a decimal digit, 0-9 — A-F have no meaning in BCD, so a BCD value containing them is invalid by definition.
Where would I need to convert BCD to hex?
Reading raw output from a real-time clock (RTC) chip or BCD-based digital display and converting it into standard hex for use elsewhere in your code.
Is BCD to hex the reverse of hex to BCD?
Yes exactly — this page takes packed decimal digits and produces true hex; Hex to BCD does the opposite.
What's the largest BCD value this handles?
There's no fixed limit — the underlying engine uses arbitrary-precision arithmetic, so BCD values of any length convert correctly.
Does BCD to hex ever change the number of digits?
No — packed BCD maps one decimal digit to one hex nibble, so the hex result always has the same digit count as the BCD input. That's different from an ordinary decimal-to-hex conversion, which usually produces fewer digits.
Why do RTC chips store time in BCD instead of plain binary?
BCD digits map directly to what a seven-segment display or a human-readable field needs — no binary-to-decimal math required on the display side, just splitting the value back into nibbles.
Can a nibble value like 0xA ever legitimately appear in BCD data?
No — a genuine BCD field only ever uses nibble values 0-9. Seeing A-F in what's supposed to be BCD data usually means it's actually packed differently, or the data is corrupted.