RGB to HEX

What is the rgb() function?

rgb() is the canonical CSS functional notation for an sRGB colour, written with three decimal channel values from 0 to 255 — for example rgb(255, 0, 0) for red. Each channel represents the intensity of one of the three additive primaries: red, green and blue. Mix all three at full strength and you get white (rgb(255, 255, 255)); set them all to zero and you get black. The notation has been in CSS since the very first colour module and is the form most often emitted by JavaScript colour libraries, design-token systems and any tool that thinks of colour as three integers rather than a packed string.

What is a HEX colour?

A hex colour is a six-digit number written in base-16 (hexadecimal) that encodes the same red, green and blue intensities as rgb() — just packed into a compact string with a leading #. The first pair of digits is the red channel, the middle pair the green channel, the last pair the blue channel, each ranging from 00 (none) to FF (255, full). So #FF0000 is rgb(255, 0, 0) — pure red. Hex has been the dominant way to write colours in HTML and CSS since 1996 because it’s compact, deterministic and trivial to paste between tools, design files and stylesheets.

The conversion math

Convert each decimal channel to a two-digit base-16 number. In JavaScript that’s n.toString(16).padStart(2, '0'): 255 becomes ff, 128 becomes 80, 26 becomes 1a, 0 becomes 00. Concatenate the three pairs in red-green-blue order, prepend #, and you have the hex string. So rgb(26, 176, 255) becomes #1AB0FF. The padding step matters — without it, rgb(5, 5, 5) would render as #555 (the three-digit shortcut for #555555, a medium grey) instead of the correct #050505, an almost-black.

Use cases

CSS authoring. Most design files, brand books and CSS frameworks emit hex. If your code is producing decimal triplets — from canvas sampling, a colour-picker library or a JSON design token — and your stylesheet convention is hex, this converter is the bridge.

Design tokens and Figma round-trips. Figma’s UI shows hex by default, so when you read RGB values from a JavaScript build pipeline and want to drop them back into a design tool, hex is usually the shorter trip.

Embedded systems and microcontrollers. Hex literals are common in C/C++ code that drives LEDs, e-ink displays and other low-level colour APIs. Converting a designer-supplied rgb() value into a hex literal (or the equivalent 0xRRGGBB integer) is the first step.

Email and CMS templates. Hex is universally supported across HTML email clients and content-management systems; if you’re templating a colour that started life as JavaScript output, the hex form is the safer paste.

Pitfalls

• Out-of-range channels. Values above 255 or below 0 aren’t valid rgb(); the converter clamps them and tells you it did. If you’re seeing clamps, your upstream source is producing values outside the 8-bit range — worth investigating.
• Float channels. Modern CSS allows percentages and floats in rgb() (e.g. rgb(50%, 0%, 100%) or rgb(255.5 0 0)). This landing rounds floats to the nearest integer before encoding, which is what every browser does internally when emitting hex.
• Alpha is dropped. rgba(r, g, b, a) input loses its alpha channel here. Use HEX to RGBA (or the Color Converter) when alpha matters.
• Named colours not accepted. red, blue, dodgerblue and the other CSS named colours aren’t parsed by this landing — paste decimal triplets only.

How to use this RGB to HEX converter

1. Paste your rgb() value into the input. The parens and commas are optional; 255, 0, 0 and rgb(255 0 0) both work.
2. The #RRGGBB output and the colour swatch update live — there is no Convert button.
3. If a channel is out of range or a value isn’t a number, a friendly inline message points at the problem.
4. Tap Copy to put the hex string on your clipboard.

Privacy

The conversion is a handful of lines of JavaScript running in your browser tab. No values are sent to a server, no analytics are attached to your colour data, and the page caches its small bundle on first load so it works fully offline afterwards.

Compatibility notes

Six-digit hex is supported by every browser ever shipped — there is no compatibility floor to worry about. The output uses the classic #RRGGBB form (uppercase by default) which is what design tools and CSS linters expect. If you need the three-digit shortcut form (#FFF instead of #FFFFFF), the Color Converter offers it as an option; this landing always emits the full six-digit form because it’s unambiguous and round-trips losslessly through every parser.