Contrast checker
Two colours in, every WCAG 2.2 contrast criterion out. Write them in
whatever your stylesheet speaks: oklch(), lab(),
color(display-p3 …), color-mix(), hex, or plain
rgb(). Everything is computed in your browser, and the
maths is the same pour engine code that audits your pages.
Checker
14.6:1
contrast ratio
Normal text, 16px. The quick brown fox jumps over the lazy dog.
Large text, 24px
Large bold, 18.66px
How to fix it
The hue and the intensity you picked survive: only lightness moves, or opacity when a translucent colour has no lightness left. Suggestions come back in the notation you typed, just past 4.5:1, the minimum for normal text.
The same pair, in every syntax
Seen with different vision
The same pair through the simulations pour tools ship. Contrast maths does not change here, but whether the two are still distinguishable does.
What this can and cannot tell you
The ratio is WCAG 2.x relative luminance, computed in sRGB exactly as
the specification defines it.
Anything you type in a wider gamut is measured on its sRGB rendering,
because that is the space the formula is defined in. A
display-p3 colour outside sRGB will show a small gamut note
rather than pretend the number covers it.
Transparency is composited before measuring, which is what a browser paints. We composite in floating point while a screen composites into 8-bit channels, so a translucent pair can differ from the rendered pixel by up to about 0.03 of a ratio point. That is never enough to change a verdict unless you are already within a rounding error of the threshold, and if you are, treat it as failing.
A ratio is not an accessibility verdict. It says nothing about whether text is legible at its size and weight, whether it sits on a photograph, or whether the two colours stay distinguishable to someone with a colour vision deficiency. For a page rather than a pair, run the extension and read what it says it cannot prove.
The same contrast code that runs in pour tools.