Hex to RGB conversion turns a CSS hexadecimal color notation, written as #RRGGBB or #RRGGBBAA, into the matching red, green, blue, and optional alpha channel bytes that a stylesheet, canvas, or display driver actually uses. Each pair of hex digits is a base-16 number from 00 to FF, which is the same range as 0 to 255 in decimal, so the converter reports an integer between 0 and 255 for each of the three color channels and for the alpha byte when one is present. A short three-digit form like #123 expands by duplicating each digit to #112233 before parsing, and a four-digit form like #0f08 expands to #00ff0088. The HEX to RGB Converter applies that expansion, parses each pair in base 16, and shows the normalized lowercase hex value, the CSS rgb() or rgba() string, the four channel bytes, and a live preview swatch so every representation of the color stays visible at once.
What Hex and RGB Each Represent
A CSS hex color is a compact string that names the brightness of three small light sources inside one screen pixel: a red sub-pixel, a green sub-pixel, and a blue sub-pixel. Each sub-pixel is dimmed or brightened independently, and the eye blends the result. Because a sub-pixel can be off, half-bright, or fully lit through many fine steps, CSS gives each channel 256 possible brightness levels, numbered 0 through 255.
Hex notation writes those same 256 levels using two characters drawn from 0 through 9 and A through F, where 00 means "no light from this sub-pixel" and FF means "as bright as this channel can go." A and a are equivalent, so #FF8800 and #ff8800 refer to the same color. This byte-level structure is why every full CSS hex color has either six or eight characters after the hash, never five or seven: two characters per channel, plus two more for alpha when transparency matters. The MDN hex-color reference and the W3C CSS Color Module Level 4 both define the syntax in the same way, and any tool that accepts a different length is bending the spec rather than following it.
The Four Accepted CSS Hex Forms
The CSS hex-color grammar accepts exactly four lengths. The converter accepts the same four, because it is built around the CSS specification rather than around whatever shorthand a particular design application might tolerate. A leading # is required in every form, and there are no spaces inside the value.
| Form | Length after # | Channels encoded | Includes alpha |
|---|---|---|---|
| #RGB | 3 digits | Red, green, blue | No (fully opaque) |
| #RGBA | 4 digits | Red, green, blue, alpha | Yes |
| #RRGGBB | 6 digits | Red, green, blue | No (fully opaque) |
| #RRGGBBAA | 8 digits | Red, green, blue, alpha | Yes |
Three- and six-digit forms do not specify alpha and are treated as fully opaque; four- and eight-digit forms carry an alpha byte and produce translucent colors. The parser duplicates each nibble in the short forms, so #abc becomes #aabbcc and #0f08 becomes #00ff0088 before any channel is read.
How to Convert Hex to RGB With the Converter
- Paste a CSS hexadecimal color beginning with # in three-, four-, six-, or eight-digit form, using only 0 through 9 and A through F with no spaces inside the value.
- Read the normalized hexadecimal value, the CSS rgb() or rgba() string, and the individual channel bytes that the converter displays.
- Check the live preview and, for translucent colors, retain the alpha byte when exact round-trip precision matters.
Channel Math: From Hex Digit to 0-255 Byte
Working through a single example makes the conversion concrete. Take the eight-digit hex color #1A2B3C80. The first pair, 1A, is the red channel. The hex digit 1 represents sixteen and the hex digit A represents ten, so 1 × 16 + 10 = 26. The second pair, 2B, is the green channel: 2 × 16 + 11 = 43. The third pair, 3C, is the blue channel: 3 × 16 + 12 = 60. The fourth pair, 80, is the alpha channel: 8 × 16 + 0 = 128.
The CSS output is therefore rgba(26, 43, 60, 0.502), and the four channel bytes are 26, 43, 60, and 128. A reader who wants the same procedure written out across several common colors can follow the worked channels and alpha values in the channel-bytes and alpha walkthrough. The endpoint rules follow from the same math: 00 always becomes 0, FF always becomes 255, and the byte value is the same number whether it is written in hex or in decimal.
Alpha Math and Round-Trip Precision
CSS alpha is not stored as a percentage. It is stored as a byte from 0 to 255, and the displayed decimal opacity is that byte divided by 255. The converter keeps three pieces of alpha information visible at once so the loss of precision stays obvious: the exact alpha byte, the rounded decimal used inside the rgba() string, and the normalized eight-digit HEX.
Take the alpha byte 80, which is 128 in decimal. Dividing 128 by 255 gives 0.5019607843, repeating. Rounded to three decimal places with trailing zeros removed, the CSS rgba() string shows 0.502. The exact byte 80 and the normalized hex value ending in 80 stay visible next to that rounded number, so a designer who needs to round-trip the color through another system can copy the byte rather than the rounded decimal and lose no precision at all. Two endpoints round cleanly: 00 stays 0 and FF stays 1, because 0 ÷ 255 and 255 ÷ 255 are both exact. Every other byte introduces a small rounding difference, which is why the normalized eight-digit HEX is the safest reference when alpha matters and the receiving system can read it.
What the Converter Rejects and Why
The parser requires a hash followed by exactly 3, 4, 6, or 8 ASCII hexadecimal digits, with no spaces inside the value. Common inputs that look fine but fail this check include a missing hash, doubled hashes such as ##FF8800, embedded whitespace such as #FF 88 00, characters outside 0 through 9 and A through F such as #GG0000, and any length that is not 3, 4, 6, or 8 characters. Ordinary whitespace around the complete value is trimmed, so a stray newline or space outside the digits will not break a valid token.
The reason for rejecting these inputs is not pedantry. CSS itself rejects them, and a tool that silently guessed what the author meant would return a color that the stylesheet would refuse to load. The W3C CSS Color Module Level 4 hex-notation section spells out the same grammar, and the strict boundary on the converter simply makes that grammar visible. Invalid or empty input also replaces the prior conversion with a clear error rather than letting a stale successful result appear to belong to the new value.
Picking the Right Output Field for the Job
Different consumers want different shapes of the same color. The converter shows all of them so the right one can be copied without recomputing by hand.
Use the individual channel bytes when an API, canvas operation, image editor, test fixture, or design token needs separate integer inputs. These are also the easiest to assert against in automated tests, because the byte range 0 to 255 is exact and platform-independent. Use the CSS rgb() or rgba() string for styles that accept CSS color functions, including inline styles, stylesheet rules, and most modern UI frameworks. Use the normalized lowercase HEX value when an exact round trip matters, especially when the alpha is not exactly representable as a short decimal.
The live preview is a sanity check, not a color-management reference. The browser renders the generated CSS color in the current document, which catches obvious mistakes such as swapped channel order, but screen profile, brightness, ambient light, and wide-gamut displays can still make the same numeric sRGB color appear different across machines. For a contrast ratio between a foreground and background, a dedicated contrast tool reads the actual luminance values rather than the byte range, and that comparison belongs in a separate workflow.
Related reading: RGB to CMYK Examples: Common Colors and the Formula.