Hex to Decimal Converter

How to convert hex to decimal

1. Give every digit its place value. Counting from the right, positions are worth 16⁰, 16¹, 16² and so on — 1, 16, 256, 4096, 65536.
2. Replace any letter with its number: A is 10, B is 11, C is 12, D is 13, E is 14, F is 15.
3. Multiply each digit by its place value.
4. Add the products together. That total is the decimal value.

The formula

For a hex number with digits d_n…d₁d₀, counting positions from zero at the right:

value = dₙ × 16ⁿ + … + d₂ × 16² + d₁ × 16¹ + d₀ × 16⁰

Nothing here is special to hex. It is the positional rule decimal already uses, with 16 in place of 10. Understand it once and you can convert from any base by hand.

Worked examples

2F
  2 × 16  =  32
  F ×  1  =  15
                 ----
                   47

1A2B
  1 × 4096 = 4096
  A ×  256 = 2560
  2 ×   16 =   32
  B ×    1 =   11
                 ------
                   6699

FFFF
  F × 4096 = 61440
  F ×  256 =  3840
  F ×   16 =   240
  F ×    1 =    15
                 -------
                  65535

The last is worth remembering on its own. Four F digits is the largest value sixteen bits can hold without a sign, and it appears constantly as a mask or a sentinel.

Quick reference

The sixteen digits below cover every conversion on this page. For every byte from 00 to FF there is a full hex to decimal table.

Prefixes: what 0x, #, $ and \x are telling you

Hex rarely appears bare. The marker in front of it is a claim about where the number came from, and recognising it saves you from converting the wrong thing.

• 0x2F — the C convention, inherited by C++, Java, Python, JavaScript, Go and Rust.
• #1A73E8 — CSS and HTML color notation. Three bytes: red, green, blue.
• $2F — older assemblers, particularly 6502 and 68000 families.
• 2Fh — the Intel assembler suffix. Same value, trailing marker.
• \x2F — a byte escape inside a string literal, not a standalone number.
• %2F — percent-encoding in a URL. This one is a forward slash.

Paste any of these above and the prefix is stripped before conversion.

Why FF matters more than 255 looks like it should

A byte is eight bits, and eight bits is two hex digits. That correspondence is why hex is everywhere in computing, and it turns certain values into landmarks.

Once FF reads as "one whole byte" rather than "two hundred and fifty-five", hex dumps stop looking like noise. Byte boundaries are visible at a glance because they are always two characters wide, which is precisely what decimal cannot give you.

Signed values and the width chips

Hex carries no sign of its own. FF is 255 if the surrounding code treats those eight bits as unsigned and −1 if it treats them as a signed byte. The bits are identical; only the interpretation differs.

That interpretation is two's complement: if the leftmost bit of the chosen width is 1, the value is negative, and you recover it by subtracting 2^width. Use the chips above the input to switch readings.

FF as unsigned  →  255
FF as int8      →  255 − 256 = −1
FF as int16     →  255   (the sign bit at position 15 is 0)

80 as unsigned  →  128
80 as int8      →  128 − 256 = −128

If a debugger and your own arithmetic disagree about a value, this is almost always why.

To do this without a tool, work through the by-hand method, which has practice problems with answers. For when each notation is the right choice, see hex versus decimal.

Frequently asked questions

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