Convert Hexadecimal to BCD

Two stages. Stage one: hex → decimal. 0xFF is 255 in decimal. Stage two: each decimal digit becomes 4 bits. 2 = 0010, 5 = 0101, 5 = 0101, so 255 in BCD is 0010 0101 0101 (12 bits for 3 digits). Unlike pure binary (where 255 would be 11111111 in 8 bits), BCD preserves each decimal digit’s identity – useful for 7-segment displays and decimal-arithmetic hardware.

Yes. The tool uses JavaScript’s native BigInt, so 16-digit hex (FFFFFFFFFFFFFFFF = 64-bit max), 32-digit hex, or arbitrarily large values convert to BCD exactly. Regular Number arithmetic would silently round past 2^53 − 1, which is only ~14 hex digits – BigInt bypasses that limitation entirely.

Because BCD uses 4 bits per decimal digit regardless of efficiency. 255 fits in 8 bits of pure binary (11111111) but needs 12 bits of BCD (0010 0101 0101) – 50% overhead. This is the trade-off: BCD makes decimal I/O simple at the cost of storage density. Pure binary is denser; BCD is easier to display.

This one (in the Binary category) is the educational quick-variant: just Packed BCD output (4 bits/digit), with a per-digit expansion in the breakdown. The Hex-category sibling adds a format selector for Unpacked BCD (8 bits/digit, zoned-decimal style) and COMP-3 (IBM mainframe signed packed with C/D sign nibble). Pick this one for learning/quick encoding; pick the sibling for mainframe integration.

Four real-world reasons. Financial arithmetic (BCD avoids binary rounding errors in money math). 7-segment display drivers on microcontrollers (each digit maps directly to a display). Legacy mainframe integration via COBOL COMP-3. Some ASIC/PLC register layouts still use BCD for parameter storage. If you’re touching hardware or old banking systems, BCD shows up.

4 × (number of decimal digits in the value). 0xFF = 255 = 3 decimal digits = 12 BCD bits. 0xFFFF = 65,535 = 5 digits = 20 BCD bits. 0xFFFFFFFFFFFFFFFF = 18,446,744,073,709,551,615 = 20 decimal digits = 80 BCD bits. The stats row tells you the digit count; multiply by 4 for bits.

Bare hex digits (FF), C-style (0xFF or 0XFF), CSS hex-color style (#DEADBEEF), with spaces (DE AD BE EF), or underscores (DE_AD_BE_EF). Case-insensitive. Batch multiple values by putting each on its own line.

Only that line fails. The breakdown panel flags it with a red border and names the offending character’s position (“Line 3: invalid hex character ‘Z’ at position 2”). Every other valid line still converts. The stats row shows how many succeeded versus failed.

No. All arithmetic runs in your browser’s JavaScript engine. No network requests fire during conversion, no server stores or logs your hex values. You can verify with your browser’s Network tab. The tool works offline after the initial page load.

Yes – the conversion is lossless. Decode the BCD nibbles back to decimal digits, concatenate them into a decimal number, then convert that to hex. our “BCD to Hex” converter (or “BCD to Decimal” → “Decimal to Hex”) handles the reverse. No precision loss in either direction.