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Complementary Color Finder

Find the complement of any colour — the hue directly opposite it on the colour wheel — with a side-by-side preview and a copyable hex. Runs entirely in your browser.

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Quick Answer

Enter a base colour and the tool returns its complement — the colour sitting directly opposite on the colour wheel. It does this by converting your colour to HSL and rotating the hue by 180 degrees while keeping saturation and lightness the same. You get both colours side by side and the complement's hex to copy. Complementary pairs sit at maximum hue contrast, which makes each colour look more vivid next to the other. It runs in your browser.

What the Complementary Color Finder Does

Give it one colour and it shows you the single colour that is its opposite on the colour wheel, displayed as a split swatch so you can see the pair together. The complement's hex code is shown ready to copy.

Complementary pairs — blue and orange, red and cyan, yellow and violet — are a staple of colour design because each makes the other appear more intense. This tool finds that partner instantly, without you having to eyeball the wheel.

How It Works

The tool converts your colour to HSL, where hue is an angle from 0 to 360 degrees around a wheel. Red sits near 0, green near 120, blue near 240. The complement is whatever hue lies exactly halfway around — 180 degrees away.

It adds 180 to your colour's hue (wrapping past 360 back to the start), keeps the saturation and lightness untouched, and converts the result back to a hex code. Because only the hue moves, the complement matches your colour in vividness and brightness — it is the same colour family member, just on the opposite side of the wheel.

Data source & conversion logic

  1. Convert to HSL. Translate the base colour into hue, saturation and lightness so the hue angle can be rotated on its own.
  2. Rotate the hue 180°. Add 180 degrees to the hue, wrapping around the 360-degree wheel, to land on the opposite colour.
  3. Keep saturation and lightness. Leave both unchanged so the complement is as vivid and as light or dark as the original.
  4. Convert back to hex. Turn the new HSL value into a hex code and show the pair as a split preview.

Complementary hue

convert base colour to HSL (hue, saturation, lightness) complement hue = (hue + 180) mod 360 saturation and lightness stay the same convert the new HSL back to hex
Worked example
base #2563EB (a blue) → complement #EBAC24 (an amber)

Adding 180 degrees lands on the opposite side of the wheel. Wrapping with mod 360 keeps the angle valid — for example a hue of 300 plus 180 becomes 120.

Standards & references

  • Complementary colours — Colours opposite each other on the colour wheel. Placed together they produce the strongest hue contrast and appear more saturated; mixed, they tend toward a neutral.
  • Colour wheel — A circular arrangement of hues. Complementary, triadic and analogous schemes are all defined by angles on this wheel — complementary being the 180-degree pair.
  • HSL colour model — Describes a colour by hue angle, saturation and lightness. It makes finding a complement a simple hue rotation.

Accuracy & Limitations

The complement is computed on the HSL/RGB wheel, which is the standard for digital colour but not identical to the traditional artists' wheel. On the classic red-yellow-blue wheel the complement of blue is orange; on the screen-based wheel blue pairs with yellow-orange. Expect the digital answer, which is what your CSS and design tools use.

It returns one strict complement — the exact opposite hue. Real palettes often prefer a split-complementary or analogous-to-complement pairing for a softer effect; this tool gives the pure 180-degree partner as a starting point.

Saturation and lightness are carried over unchanged, so a pale base gives a pale complement and a vivid base a vivid one. That keeps the pair balanced, but if you want a light-and-dark contrast you will adjust lightness yourself afterwards.

A complementary pairing maximises hue contrast, but that is not the same as accessible text contrast. Two complements with similar lightness can be hard to read as text on each other — check any such pair in a contrast checker.

Real-World Use Cases

Choosing an accent colour

Pair a brand colour with its complement for buttons or highlights that pop.

Designing a two-colour scheme

Start a palette from a base and its opposite.

Making elements stand out

Place a colour on its complement for maximum visual contrast.

Learning colour theory

See exactly which colour sits opposite any hue on the wheel.

When to use it — and when not to

Good for

  • Finding the opposite colour on the wheel
  • Starting a complementary two-colour scheme
  • Picking a high-contrast accent
  • Understanding colour relationships

Not the best choice for

  • Split-complementary or triadic schemes
  • A full multi-colour palette
  • Guaranteeing readable text contrast
  • Traditional artists' (RYB) pairings

For a fuller scheme, use a colour palette generator (analogous, triadic, monochromatic). For text legibility on the pair, check it in a contrast checker. For tints and shades of either colour, use a shades generator.

Frequently Asked Questions

What is a complementary colour?
The colour directly opposite a given colour on the colour wheel. Complementary pairs sit at the greatest hue contrast, so each makes the other look more vivid when they are placed together.
How is the complement calculated?
Your colour is converted to HSL and its hue is rotated by 180 degrees around the wheel, keeping saturation and lightness the same, then converted back to a hex code.
Why is the complement of blue shown as amber, not orange?
This uses the digital RGB/HSL colour wheel, where blue sits opposite a yellow-orange. The traditional artists' (red-yellow-blue) wheel pairs blue with orange. CSS and design software use the digital wheel, which is what this tool reports.
Do saturation and lightness change?
No. Only the hue is rotated; saturation and lightness are carried straight over. So a muted base gives a muted complement, and a bright base a bright one.
What is the difference from a split-complementary scheme?
A strict complement is the single opposite hue. Split-complementary uses the two hues either side of that opposite, for a gentler, more flexible pairing. This tool gives the strict complement; you can step a little either side for split-complementary.
Will a complementary pair always be readable as text?
Not necessarily. Maximum hue contrast is not the same as the lightness contrast text needs. If the two colours have similar lightness, text in one on the other can be hard to read — verify it against the WCAG ratios in a contrast checker.
What happens if I mix the two complements?
Complements mixed together tend toward a neutral grey or brown, because between them they cover the whole hue circle. That is why complements are used side by side for contrast, not blended.
Can I get the complement of white, black or grey?
Greys (including white and black) have no real hue, so rotating the hue leaves a grey of the same lightness. The complement of a neutral is essentially the same neutral.
How do I copy the complement?
The complement's hex code is shown next to the swatch; click to copy it and paste into your CSS or design tool.
Is this the same as inverting a colour?
No. Inverting flips each RGB channel (255 minus the value), which changes hue, saturation and lightness together. A complement rotates only the hue by 180 degrees and keeps the rest, so the two usually give different results.
Is my colour sent anywhere?
No. The complement is worked out in your browser; nothing about your colour leaves your device.
Why use complementary colours at all?
They create strong, energetic contrast and draw the eye — useful for a call-to-action against a brand colour. Used in large amounts they can feel intense, so many designs use one as the dominant colour and the complement as an accent.

References

Derives the complement by rotating the hue 180° in HSL while keeping saturation and lightness; honest that this is the classic opposite-hue pairing, not a perceptual or split-complementary scheme.

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