What LRV means
Light reflectance value, or LRV, measures how much light a colour reflects, on a scale from 0 for absolute black to 100 for perfect white. Paint makers print it on their colour chips and websites. It is the most useful single number for predicting how light or dark a colour will look on your walls.
How to read the number
Colours above about 60 are light and keep a room bright, which helps small and north-facing rooms. Colours between about 30 and 60 are mid-tones that look true in good light and darker in dim rooms. Below about 30 is dark: dramatic, but it needs good light and often an extra coat to cover evenly.
How this calculator estimates it
It converts the hex code into the relative luminance of that colour as displayed on screen, which closely tracks LRV. Screens, printing and the paint itself all differ slightly, so the manufacturer’s published LRV is the official figure. Use this to compare colours and to estimate LRV when you only have a hex code.
Undertone
The undertone hint shows whether the colour leans warm, towards yellow, red or beige, or cool, towards blue, green or grey. Undertones show most in white and grey paints; compare samples on your own wall in morning and evening light before you buy.
Results are estimates. Coverage depends on the product, the tools and the wall; the rate printed on your can wins.