NuteLch measures chroma relative to the gamut shell — the cusp — in OKLCH and LCH. You ask for a fraction of the way to the boundary (relC) instead of an absolute chroma, so “saturation” means the same thing at every lightness and hue and never accidentally lands out of gamut, while the result stays a native oklch() / lch() color. It's dependency-free and LUT-backed: the boundaries are precomputed, so lookups are fast. nutelch on GitHub →

• …× faster than culori, benchmarked live in your browser right now
• …gamut-boundary lookups per millisecond, here
• …× faster than OkHSL at producing a boundary-relative color
• …worst-case boundary error vs the true sRGB gamut, measured live