By Mark Kotterink, director of the Dutch Colour Institute (SNKI) · Published 21 October 2026 · Updated 21 October 2026
Light reflectance value (LRV) explained for architects
LRV is the share of visible light a surface reflects, from 0 (black) to 100 (perfectly white). White paint is usually above 80.
The light reflectance value, LRV for short, tells you how much light a surface reflects. For architects it is a practical figure. It determines the contrast for people with low vision, how bright a room becomes and how much artificial light you need.
What is LRV?
LRV stands for light reflectance value. The figure states what share of visible light a surface reflects, weighted by the sensitivity of the eye. The scale runs from 0 (all light absorbed) to 100 (all light reflected). In practice no material reaches those extremes: black is always above 0 and white never reaches 100. White paint is usually above 80, deep black below 10.
Technically, LRV is the Y value of the CIE colour system (XYZ). Test reports to the British measurement standard BS 8493 use illuminant D65 and the 10° observer, with the specular gloss included in the measurement.
Why LRV matters
Facades add another factor. A light facade heats up less in the sun than a dark one. LRV only covers visible light; infrared also counts for heat. So use LRV as an indication there, not as a calculation value.
Contrast: the 30-point rule of thumb
You express lightness contrast as the difference between two LRV values. In the British guidance BS 8300, a difference of at least 30 points between adjacent surfaces counts as adequate visual contrast. A floor with LRV 20 and a wall with LRV 55 differ by 35 points and meet that.
Which requirement applies to your project depends on the regulations and on the guideline the client prescribes. Check this beforehand. This page does not replace a standard.
LRV and the NCS code
The NCS code describes how a colour looks: blackness (s), chromaticness (c) and hue. LRV is a measured figure. They are related, but they are not the same.
- Within the same hue and chromaticness, more blackness means a lower LRV. S 1000-N reflects more light than S 5000-N, and S 5000-N more than S 9000-N.
- High whiteness, meaning little blackness and little chromaticness, means a high LRV. Whites are usually above 80.
- Hue counts as well. S 2050-Y and S 2050-B have the same blackness and chromaticness, but the yellow reflects far more light than the blue.
NCS also has its own measure of lightness, NCS lightness (v). The NCS Lightness Meter shows it next to the Y value, so you see both side by side.
Do not use a table of LRV values per colour code as evidence for a project. Paint, gloss level and substrate change the real value. Ask the manufacturer for the measured LRV of the product, or measure it yourself.
Rules of thumb for design
- 1Ceiling the lightestLighting standards for workplaces, such as EN 12464-1, give recommended reflectance ranges for the main surfaces: the ceiling highest, the floor lowest. Look up the figures in the edition that applies to your project.
- 2Contrast where it mattersProvide a clear LRV difference at doors and frames, stairs and stair nosings, the junction of wall and floor, controls and obstacles.
- 3Not everything equally lightA room in which everything is equally light is hard to read for people with low vision. A darker floor or skirting gives guidance.
- 4Mind the glossGlossy surfaces mirror lamps and windows. Those reflections can cancel out the contrast. Matt finishes are calmer.
- 5Put it on recordState in the specification, per surface, the NCS code, the gloss level and the required LRV or LRV difference.
How to measure LRV
You measure LRV with a colorimeter or spectrophotometer that gives the Y value, or that gives L* under D65 with the 10° observer. From L* you calculate the Y value yourself:
According to NCS, the NCS Colourpin PRO measures with a sphere geometry (d/0) including specular gloss and gives Lab values under D65 with the 10° observer. That matches the way LRV is measured. For an official declaration, for example in a tender, ask for a test report to the prescribed method.
Want a quick estimate without electronics? The NCS Lightness Meter is a card with 18 grey samples with round viewing holes. You look for the grey that appears as light as the surface and read off the corresponding NCS lightness and Y value.
Frequently asked questions
What is a good LRV for a wall?
That depends on the function. Light walls reflect more light and make a room brighter; whites are usually above 80. More important than the value itself is often the difference from the floor, doors and ceiling. As a rule of thumb, aim for at least 30 points.
Is LRV the same as NCS blackness?
No. Blackness describes how black a colour looks; LRV is measured reflected light. Within one hue and chromaticness, LRV falls as blackness rises. But S 2050-Y and S 2050-B, with the same nuance, have very different LRVs: yellow reflects far more light than blue.
Can I calculate LRV from L*a*b*?
Yes, from L* alone. The formula is Y = 100 × ((L* + 16) / 116)³, valid for L* above 8. Use L* measured under D65 with the 10° observer and with gloss included. For an official declaration, ask for a test report.
Why is there no LRV table per NCS colour here?
Because a table value says little about your project: paint, gloss level and substrate change the real value. Ask the producer for the measured LRV of the product or measure the finished surface. A colour reader or the NCS Lightness Meter helps with that.
Does the 30-point rule apply outside the UK?
The rule comes from British guidance such as BS 8300. It is a useful rule of thumb, but which requirement applies to your project depends on the regulations and on the guideline the client uses. Always check this beforehand.
Mark Kotterink, director of SNKI. Colour expert, lecturer and researcher with 35 years of experience in colour technology and colour application.