Short answer: light dose is lux multiplied by hours, so a wall's yearly dose is lux x lit hours a day x lit days a year. This calculator does that sum for two walls and shows how much more one receives than the other. Equal doses are treated as equal damage in the museum guidance our guide reports, so the useful result is a comparison between options, not a date on which a print will fade.
Compare the yearly dose of two walls
The published examples, and one changed figure
| Lux | Hours lit | Dose (lux x hours) | Basis |
|---|---|---|---|
| 100 | 400 | 40,000 | Canadian Conservation Institute example, as reported on our lux-hours guide |
| 50 | 800 | 40,000 | Canadian Conservation Institute example, as reported on our lux-hours guide |
| 50 | 1,000 (10 a day for 100 days) | 50,000 | NEDCC example, as reported on our lux-hours guide |
| 100 | 1,000 (same hours as the NEDCC example) | 100,000 | Arithmetic only: doubling the lux doubles the dose |
Four steps, as on our guide
- Find the lux on the wall with a light meter, or ask the lighting supplier, because the lux depends on your own lamps, distance and daylight.
- Count every hour the light is on, not only opening hours; housekeeping and openings add lit time. Daylight is harder to count because it changes with the time of day, the season and the weather.
- Count the days per year the light is on.
- Multiply, then repeat the sum with a changed lux or changed hours and compare the two totals.
What the number does not tell you
- It does not give a fade time for any print or ink. The sources describe the principle for planning; treat the result as a way to compare options.
- NEDCC suggests an annual exposure of 50,000 lux-hours as an ideal for light-sensitive materials. That is a museum ideal for sensitive collections, not a rule for commercial walls.
- A UV filter removes only part of the problem. For colours sensitive to light, the Canadian Conservation Institute puts UV at usually under half of the fading, so the visible light you leave on still counts.
- Light damage is cumulative and cannot be undone, so plan the dose before the pieces go up.
Download the wall light budget worksheet (CSV)
The CSV has one line per wall and a dose column that multiplies the three numbers when opened in a spreadsheet. Related: lux-hours: how light dose adds up on a wall, light, UV and fading of printed artwork on walls, planning wall art for hotel rooms, conservation and light terms.
If your artwork will hang in a bright or long-lit space, tell us the setting and the daily lit hours in your enquiry, so we can discuss it before the quote.
Start an enquiry when your brief is ready; we reply within 1 business day, with questions or a quote.
Sources: lux-hours and how light dose adds up on a wall [S36]. As of 2026-11-12. Terms are typical and are confirmed in your written quote.