LRV calculator
Only have a paint’s HEX or RGB? Type it below to get its approximate light reflectance value (LRV): the share of visible light a surface reflects, from 0 for black to 100 for white. Mid grey #808080, for example, comes out at 21.6. The second color gives the LRV difference against the 30-point rule for visual contrast in buildings, and the same pair under the US, Australian and German rules. If the paint chip prints a measured LRV, type that number instead: it beats any screen color.
Two surfaces
LRV ≈ 60.1 from the screen color
LRV ≈ 10.2 from the screen color
Marks +15, +20 and +30 are the thresholds counted up from the darker surface. ✓ means the lighter surface reaches that mark.
Screen colors only, so this is a guide, not a compliance check. A paint or a floor finish has its own measured LRV, printed on the chip or in the maker’s data sheet: type it in above for a real surface.
| Approved Document M threshold | LRV difference | This pair |
|---|---|---|
| The general rule | > 30 | ✓ enough |
| Where the light on the surfaces is above 200 lux | ≥ 20 | ✓ enough |
| For door opening furniture that projects or otherwise creates enhanced differentiation and shade | ≥ 15 | ✓ enough |
«More than 30» means 30.0 itself is not enough; 20 and 15 are minimums, so 20.0 and 15.0 are. Here and in the table below, values are checked before rounding: when rounding would land one on a threshold, it is shown with more decimals, such as 19.97. Don’t know the light level on the surfaces? Go by the general rule: it is the strictest of the three.
This pair under each standard
| Standard | Formula | This pair | Needs | Result |
|---|---|---|---|---|
| Approved Document M, vol. 2 | LRV difference | 49.9 points | > 30 points | ✓ passes |
| 1991 ADAAG, appendix A4.30.5 (signs) | Weber | 83.0% | ≥ 70% | ✓ passes |
| ICC A117.1-2026, 703.2.10.2.2 (signs) and 505.10.1 (stair markings) | Weber | 83.0% | ≥ 65% | ✓ passes |
| AS 1428.1-2009 | Bowman–Sapolinski | 65.4% | ≥ 30% | ✓ passes |
| AS/NZS 1428.4.1, tactile indicators: integrated | Bowman–Sapolinski | 65.4% | ≥ 30% | ✓ passes |
| AS/NZS 1428.4.1, tactile indicators: discrete | Bowman–Sapolinski | 65.4% | ≥ 45% | ✓ passes |
| AS/NZS 1428.4.1, tactile indicators: composite discrete | Bowman–Sapolinski | 65.4% | ≥ 60% | ✓ passes |
| DIN 32975:2009-12 (controls, orientation and guidance systems) | Michelson K | K 0.71; lighter LRV 60.1 | K ≥ 0.40 and lighter LRV ≥ 50 | ✓ passes |
Each standard has its own formula, so one pair can pass one and fail another. The formulas are explained below the calculator.
How the LRV is estimated
Light reflectance value is the CIE Y value of a surface on a 0–100 scale. For a color on screen, Y comes from its sRGB values: the same relative luminance the contrast checker uses, times 100. For the color on screen this is a calculation, not an approximation; the estimate comes in when the screen color stands in for a real surface.
It is not the measured LRV of a paint. BS 8493 measures a real surface under the D65 illuminant with the 10° observer and includes the gloss, while sRGB is defined with the 2° observer, and a HEX on a website is only a picture of the paint. Treat the number as an estimate for comparing colors, and take the maker’s published LRV for anything that will be built.
One pair, different standards
All of these rules start from the same two LRV numbers, then put them through different formulas. Below, «lighter» and «darker» are the two LRVs on the 0–100 scale.
- LRV difference, lighter − darker: Approved Document M in England, more than 30 points.
- Weber, (lighter − darker) / lighter × 100: the 1991 ADA guidelines for signs, 70%, in an advisory appendix; ICC A117.1-2026, 65% for most signs and stair-nosing markings.
- Bowman–Sapolinski, 125 × (lighter − darker) / (lighter + darker + 25): AS 1428.1-2009 in Australia, 30% (the 2021 edition replaced it; we have not confirmed its formula); for tactile ground indicators under AS/NZS 1428.4.1, council specifications quote 30% (integrated), 45% (discrete) or 60% (composite discrete).
- Michelson, (lighter − darker) / (lighter + darker): DIN 32975 in Germany, K at least 0.40 for controls and guidance systems, and the lighter surface must reflect at least half the light (LRV 50 or more).
On light colors the formulas disagree a lot. Warm grey #D1CBC1 against white #FFFFFF is 60.1 against 100.0: 39.9 points apart, which passes the UK rule, but only 26.9% by Bowman–Sapolinski, so it fails AS 1428.1. Weber gives 39.9% and Michelson K = 0.25: it fails the US and German rules too.
Weber and Michelson have the opposite trap with dark colors: a darker LRV of 0 makes any pair score 100%. Navy #000080 against black #000000 gets 100.0% by Weber and K = 1.00, though the two are only 1.6 points apart. Real surfaces never reach 0, which the 1991 ADA appendix itself points out, and DIN 32975’s rule that the lighter surface reach LRV 50 rejects this pair. Bowman–Sapolinski gives it 7.3%.
Not in the table: the EU rail rule (PRM TSI), whose current application guide points to paywalled EN and ISO standards for the contrast method; the French 70% rule, whose formula we could not confirm; and any other DIN 32975 thresholds. The thresholds above were checked against the sources listed at the bottom of the page.
LRV of greys
LRV does not run evenly with how light a grey looks: the middle of the HEX scale, #808080, reflects only about a fifth of the light. Against screen white (LRV 100) a grey passes the 30-point rule only below LRV 70: #E0E0E0 (74.5) is not enough, #C0C0C0 (52.7) is.
| Color | LRV (screen) |
|---|---|
| #FFFFFF | 100.0 |
| #E0E0E0 | 74.5 |
| #C0C0C0 | 52.7 |
| #A0A0A0 | 35.2 |
| #808080 | 21.6 |
| #606060 | 11.7 |
| #404040 | 5.1 |
| #202020 | 1.4 |
| #000000 | 0.0 |
LRV: questions
- What is LRV?
- Light reflectance value: the share of visible light a surface reflects, on a scale from 0 (absorbs everything) to 100 (reflects everything). Real surfaces never reach exactly 0 or 100: even the deepest black reflects a little light, and no white reflects all of it.
- How is LRV calculated from a color?
- LRV is the CIE Y value of the color times 100. For a screen color that is the relative luminance WCAG uses, from the sRGB values: each channel is linearised, then Y = 0.2126 R + 0.7152 G + 0.0722 B. The British test method BS 8493 measures Y of the real surface with the D65 illuminant and the 10° observer; sRGB uses the 2° observer, so the number here is an estimate.
- What LRV difference do I need for accessibility?
- In England, Approved Document M (volume 2, buildings other than dwellings) defines visual contrast as an LRV difference greater than 30 points between two surfaces. Where the light on the surfaces is above 200 lux, at least 20 points. Where door opening furniture projects beyond the face of the door or otherwise creates enhanced differentiation and shade, a difference of at least 15 points is considered adequate. If you do not know the light level, go by the general rule: it is the strictest. On screen, white #FFFFFF has an LRV of 100, so a color needs an LRV below 70 to pass the 30-point rule against pure white.
- How can I find the LRV of a paint color if I only have its HEX or RGB?
- Type the HEX code or the RGB values into the calculator above: it returns the LRV of that color on screen, its CIE Y times 100. For example, #D1CBC1 gives an LRV of about 60.1. Treat it only as a rough guide: a HEX copied from a paint maker’s website is a screen picture of the paint, not a measurement, and screens differ. Paint makers publish the measured LRV of each color on the chip or in the data sheet; for a building, type that number into the «maker’s measured LRV» field instead.
- Why does one color pair pass in the UK and fail in Australia?
- Because the two use different formulas. Approved Document M takes the plain LRV difference; AS 1428.1 uses the Bowman–Sapolinski formula, 125 × (lighter − darker) / (lighter + darker + 25), which asks more of two light colors. On screen, #D1CBC1 against white #FFFFFF is 39.9 points apart, which passes the UK rule of more than 30, but scores 26.9% by Bowman–Sapolinski, short of the Australian 30%.
- What contrast does the ADA require for signs?
- The 1991 ADA Accessibility Guidelines gave a 70% figure, with the formula (B1 − B2) / B1 × 100, but only in the advisory appendix (A4.30.5). The 2010 ADA Standards (703.5.1) give no number: characters must be light on a dark background or dark on a light one. The new ICC A117.1-2026 standard sets 65% with the same formula for most signs and for stair-nosing markings; it applies where a state or city adopts a building code that references it.
- Why does a color against black score 100%?
- The Weber formula (ADA, A117.1) divides by the lighter LRV, and Michelson (DIN 32975) by the sum, so a darker LRV of 0 gives 100% or K = 1 for any color at all. On screen, navy #000080 against black #000000 scores 100.0% and K = 1.00, though they are only 1.6 LRV points apart. Real surfaces never reach 0: the 1991 ADAAG itself notes that black is never absolute. DIN 32975 also requires the lighter surface to reflect at least half the light, and Bowman–Sapolinski adds 25 below the line, which gives this pair only 7.3%.
- Is LRV the same as lightness L*?
- No. L* is a perceptual scale and runs higher: a grey with LRV about 18 has L* about 50, so it looks halfway between black and white. The HEX midpoint #808080 is a little lighter than that: LRV 21.6, L* about 54. LRV is the plain share of light reflected, which is what the building guidance uses.
Sources
- HM Government. Approved Document M, volume 2: Buildings other than dwellings, 2015 edition incorporating 2020 and 2024 amendments (England), 0.26 definitions «Contrast visually» and «Light reflectance value». Link
- Desso (Tarkett). Technical LRV sheet: LRV measured to BS 8493:2008 with standard illuminant CIE D65 and the 10° standard colorimetric observer. Link
- W3C (2018, current edition 6 May 2025). Web Content Accessibility Guidelines (WCAG) 2.1: definitions of relative luminance and contrast ratio, success criteria 1.4.3 and 1.4.6. Link
- U.S. Access Board. ADA Accessibility Guidelines (ADAAG), 1991 edition as amended through September 2002: appendix A4.30.5 «Finish and Contrast» (70 percent, Contrast = [(B1 − B2)/B1] × 100) and the appendix preamble «materials of an advisory nature». Link
- U.S. Access Board. 2010 ADA Standards for Accessible Design, 703.5.1 Finish and Contrast: light characters on a dark background or dark characters on a light background; no numeric value. Link
- ICC A117 Consensus Committee. ICC A117.1 Accessible and Usable Buildings and Facilities, final ballot clean draft for vote dated 10-5-2025 (comments closed 5 Nov 2025): 703.2.10.2.2 (signs, 65 percent minimum) and 505.10.1 (stair visual contrast markings, 65% minimum), Contrast = [(B1 − B2)/B1] × 100; LRV equivalent to CIE Y. Link
- Paarlberg K. (19 May 2026). A117.1-2026: The International Code Council to Release Major Updates to the Nation’s Leading Accessibility Standard. ICC Building Safety Journal: new edition in fall 2026, referenced in the 2027 International Codes. Link
- Sapolinski J., Garth S. M., Garth I. M. An improved metric for luminance contrast using colour-modified clinical eye charts: the Bowman–Sapolinski equation, adopted in AS 1428.1-2009. Link
- Braille Tactile Signs (Aust). Luminance contrast: C = 125 (Y2 − Y1)/(Y1 + Y2 + 25), Y1 the darker, per AS 1428.1 (2009) part B4 and AS/NZS 1428.4.1 (2009) E3/E5; 30% minimum. Link
- Wyndham City Council (October 2021). Specification No 799, Tactile Ground Surface Indicators, 2.8.2: luminance contrast to AS/NZS 1428.4.1 Appendix E; 30% integrated, 45% discrete, 60% composite discrete TGSIs. Link
- Schlanke M., Vandahl C., Bieske K., Schierz C., Kolbe O., Gebhardt M., Kunert K. (2023). Untersuchungen zur Optimierung von barrierefreien visuellen Kontrasten. 16. Internationales Forum für den lichttechnischen Nachwuchs, Ilmenau: quotes DIN 32975:2009-12 (Michelson contrast, at least 0.4 for controls, orientation and guidance systems). DOI
- Deutscher Blinden- und Sehbehindertenverband, leserlich.info. Kontrastrechner: DIN 32975 uses the Michelson formula on Y values; the lighter colour must reflect at least 50% of the light. Link
- TU Chemnitz, Leit- und Orientierungssystem: Barrierefreiheit nach DIN 32975 — not an introduced technical building rule, so not legally binding; its use must be agreed by contract. Link