RGB to HEX Converter

Going from RGB to hex is the direction most people hit after picking a color visually rather than typing one in: a design tool’s eyedropper or slider hands you three numbers — red, green, blue, each 0-255 — and the next step is almost always turning that into the compact hex string CSS, config files, and style guides actually expect. rgb(220, 38, 38) and #dc2626 are the exact same color; hex is just a shorter way to write the same three numbers.

The arithmetic runs in the opposite direction from parsing hex: instead of splitting a string into pairs and reading each as a base-16 number, each 0-255 channel gets converted to a 2-digit base-16 (hexadecimal) pair and the three pairs are joined together. 220 in hexadecimal is dc; 38 is 26; concatenating dc + 26 + 26 gives #dc2626. Every possible 0-255 value has exactly one 2-digit hex representation, so unlike converting through HSL (where hue/saturation/lightness get rounded to whole numbers for display), this conversion loses no precision in either direction.

One detail worth knowing when you’re staring at the result: not every hex code can be shortened to the familiar 3-digit form. That shorthand only exists when each channel’s two digits happen to be identical — #33aaff can shorten to #3af because 3=3, a=a, f=f, but a color like #dc2626 can’t, because d ≠ c in the first pair. Most real-world colors picked from a design tool land on non-repeating digit pairs and simply don’t have a shorter form — that’s not a bug in a particular converter, it’s just how often the coincidence of matching digits actually happens (1 in 16 per channel).

Converting RGB to hex programmatically

JavaScript — the same technique browser DevTools and design tools use internally to display a picked color as hex:

function rgbToHex(r, g, b) {
  const toHex = (n) => Math.max(0, Math.min(255, n)).toString(16).padStart(2, "0");
  return `#${toHex(r)}${toHex(g)}${toHex(b)}`;
}

console.log(rgbToHex(220, 38, 38));
// "#dc2626"

Python, using an f-string’s built-in hex formatting instead of a manual toString:

def rgb_to_hex(r, g, b):
    r, g, b = (max(0, min(255, v)) for v in (r, g, b))
    return f"#{r:02x}{g:02x}{b:02x}"

print(rgb_to_hex(220, 38, 38))
# "#dc2626"