Convert Hex to Decimal

Each hex digit is a position in base 16. The rightmost digit contributes its value × 16⁰, the next × 16¹, and so on. 0xFF = 15×16¹ + 15×16⁰ = 240 + 15 = 255. This tool uses JavaScript’s native BigInt, so the math is exact for any input length.

Unsigned treats the hex as a non-negative magnitude – 0xFF is just 255. Signed (two’s complement) interprets the high bit as a sign bit. For 8-bit signed, 0xFF is −1 (because all bits set means “all magnitude subtracted”), 0x80 is −128, 0x7F is +127. This matches how CPUs encode negative integers.

Because the sign-bit position depends on width. 0xFF at 8-bit is −1, but 0x00FF at 16-bit is +255 – same numeric value, different interpretation. Without an explicit width, the tool has to guess from digit count, which can confuse users. “Auto” mode uses nibble-count × 4 (so FF → 8-bit, FFFF → 16-bit); switch to a fixed width when you know your target’s register size.

Yes. JavaScript’s native BigInt has no upper bound – 256-bit or 1,024-bit hex values produce their exact decimal representation. Regular Number arithmetic would silently round off anything past 9,007,199,254,740,991 (2⁵³ − 1), which you’d hit with any 14+ digit hex. BigInt is the only safe choice for this.

Bare digits (FF), C-style prefix (0xFF or 0XFF), with spaces (FF 00), with underscores (DE_AD_BE_EF), across multiple lines, or any combination. Case-insensitive – aBc and ABC and Abc all decode identically.

You get an error naming the overflow. For example, setting width to 8-bit and entering 0x1FF (9 bits needed) will fail with “Value 0x1FF (511) exceeds chosen 8-bit width (max 255).” Auto mode doesn’t have this restriction because it derives the width from your input.

Each successfully converted value shows its bit pattern (binary, with leading zeros preserved to fill the chosen bit width) and its octal form. This is useful when the same value is needed in multiple bases – you can grab all three from one conversion, no round-trip through separate tools.

When each line of input is a separate hex value – for example a column of pointer addresses from a debugger, or the contents of a memory dump. Batch mode processes each line independently, so a typo on one line doesn’t break the others. Invalid lines appear in the error list below the breakdown.

No. All arithmetic runs in your browser’s JavaScript engine – no network requests fire during conversion, no cookies are set, no analytics are sent. You can verify with your browser’s Network tab. The tool keeps working after you disconnect from the internet.

Yes – the conversion is lossless in both directions. Use our “decimal to hex” converter (or Python’s hex(), or JavaScript’s .toString(16)). For signed values, make sure the decimal-to-hex tool you pick knows which bit width to encode at, otherwise small negative numbers come back ambiguous.