Illumination / lx → ph
Convert Lux to Phot
Convert illuminance on a surface between lux and foot-candles. Convert Lux (lx) to Phot (ph). Find the formula, worked examples, unit definitions, and practical guidance below.
How to convert lux to phot
Illuminance is luminous flux per area, not radiant watts per area. One lux is one lumen per square meter. Photometric weighting prevents a universal lux-to-watts conversion.
Use x for the value in lx, b for the intermediate value in lx, and y for the result in ph.
ph = lx ÷ 10000
Worked examples
10 lx ≈ 0.001 ph
Step 1: (10 × 1) ≈ 10 lx.
Step 2: 10 ÷ 10000 ≈ 0.001 ph.20 lx ≈ 0.002 ph
Step 1: (20 × 1) ≈ 20 lx.
Step 2: 20 ÷ 10000 ≈ 0.002 ph.
Results are rounded to 12 significant digits. Converting units does not increase the precision of the original measurement. Very large or small values outside JavaScript’s finite numeric range are rejected.
About Lux
Lux (lx) measures illumination under the conventions above. The base value in lx is (x × 1), where x is the numerical value in lx. Factors shown here are rounded for display; calculations use the stored factor.
About Phot
Phot (ph) measures illumination under the conventions above. The base value in lx is (x × 10000), where x is the numerical value in ph. Factors shown here are rounded for display; calculations use the stored factor.
Definitions and sources
Carry the same physical assumptions into subsequent physics calculations.
Lux to phot reference table
| Lux (lx) | Phot (ph) |
|---|---|
| 1 | 0.0001 |
| 5 | 0.0005 |
| 10 | 0.001 |
| 25 | 0.0025 |
| 50 | 0.005 |
| 100 | 0.01 |
| 1000 | 0.1 |
Browse every illumination conversion →