Convert Phots to Lumens per square inch
Convert Phots (ph) to Lumens per square inch (lm/in²) instantly and accurately.
Conversion Formula
lm/in² = ph × 6.4516
About Phots
The phot (ph) equals 1 lm/cm² = 10 000 lx. The CGS-photometric unit of illuminance. Pre-SI optics texts express daylight in phots: full tropical sunshine is ~10 ph (100 klx); overcast sky ~0.1-0.2 ph. Wholly superseded by lux and kilolux in modern standards. 1 ph = 10⁴ lx.
About Lumens per square inch
The lumen per square inch (lm/in²) equals 1/0.00064516 lx ≈ 1 550 lx. Used in US optics and LED backlight datasheets when specifying output over small aperture areas. Rare in general lighting but found in US optical engineering catalogs and LCD backlight specifications. 1 lm/in² = 1/0.00064516 lx.
Quick Reference Table
| Phots (ph) | Lumens per square inch (lm/in²) |
|---|---|
| 1 ph | 6.4516 lm/in² |
| 2 ph | 12.9032 lm/in² |
| 5 ph | 32.258 lm/in² |
| 10 ph | 64.516 lm/in² |
| 25 ph | 161.29 lm/in² |
| 50 ph | 322.58 lm/in² |
| 100 ph | 645.16 lm/in² |