What is the ANSI 256-color palette?

It is the standard extended color set most terminals support. Codes 0 to 15 are the system and bright colors, codes 16 to 231 form a 6×6×6 RGB cube, and codes 232 to 255 are a 24-step grayscale ramp. Together they give 256 selectable colors.

How does the tool find the nearest color?

It computes the exact RGB value of all 256 palette entries, then measures the squared Euclidean distance from your hex color to each one and returns the entry with the smallest distance. If the distance is zero, your color is an exact palette match.

How do I use the resulting code in a terminal?

Wrap the code in an escape sequence. For text color use ESC[38;5;Nm and for background use ESC[48;5;Nm, where N is the code. Reset afterwards with ESC[0m. The ESC character is the literal escape byte, often written \e or \033.

How are the cube colors calculated?

For codes 16 to 231 the index minus 16 splits into red, green and blue levels of 0 to 5. Each non-zero level maps to the value 55 plus 40 times the level, while level 0 maps to 0. That non-linear step is why the cube is not a simple even spread.

Why is my color only approximate?

The 256-color palette is a fixed grid, so most arbitrary hex colors fall between palette points. The converter returns the perceptually nearest available code, but for true color you can use a terminal that supports 24-bit ANSI with the ESC[38;2;R;G;Bm sequence instead.

ANSI Color Code Converter

Map any hex color to the closest terminal color

The ANSI Color Code Converter finds the nearest entry in the ANSI 256-color palette for any hex color and gives you the escape sequences to use it. It is the quick way to translate a brand color or design swatch into something your shell scripts, CLI tools and terminal UIs can actually display.

How it works

The 256-color palette is three regions with precise RGB definitions:

Codes 0–15: the fixed system and bright colors (black, red, green, … white).
Codes 16–231: a 6×6×6 cube where index = 16 + 36·r + 6·g + b and each channel level maps to 0 for level 0 or 55 + 40·level otherwise.
Codes 232–255: a grayscale ramp where each step is 8 + 10·(index − 232).

The converter generates the exact RGB for all 256 codes, then computes the squared distance dr² + dg² + db² between your color and each palette entry, returning the code with the smallest distance. A distance of zero means an exact match.

Example

The color #3366ff is not on the palette grid, so the tool returns the nearest cube code and reports it as a close approximation, showing both swatches side by side. To use it as text color you would write the escape sequence \e[38;5;Nm before your text and \e[0m after to reset.

Notes

Because the palette is a coarse grid, expect approximations for most arbitrary colors. If your terminal supports 24-bit “true color”, you can sidestep the palette entirely with the \e[38;2;R;G;Bm sequence and your exact RGB values.