ph to lx Converter

Convert Phot to Lux instantly.

Free online converter with accurate results and clear explanations.

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How This Tool Works

The Phot to Lux Converter uses the standard illuminance relationship: 1 phot = 10,000 lux. Enter a value in phots and the calculator multiplies it by 10,000 to show the equivalent value in lux.

The swap control reverses the calculation so you can convert lux back to phots by dividing by 10,000.

  • Input: Phots (ph) or lux (lx), depending on the selected direction.
  • Conversion factor: 1 ph = 10,000 lx.
  • Output: Equivalent illuminance in the opposite unit.

Why This Matters in Lighting Design

Phot and lux both measure illuminance: how much visible light falls on a surface. Lux is the SI unit used in most lighting specifications, while phot is a CGS unit that may appear in older references or specialized engineering material.

Converting phot values to lux keeps calculations aligned with common lighting targets, building guidance, and fixture documentation.

Common Mistakes to Avoid

  • Do not confuse phot with foot-candles: 1 phot equals 10,000 lux, while 1 foot-candle is about 10.764 lux.
  • Keep illuminance separate from lumens: Lux and phot measure light on a surface; lumens measure total light output from a source.
  • Round after converting: Keep enough precision for engineering notes or code checks before formatting the final value.

Frequently Asked Questions

Common questions about the ph to lx Converter

Lumens measure total light output from a source, while lux measures light intensity at a surface. Lux = lumens per square meter.
Learn More

Sources & References

International System of Units (SI): luminous intensity and illuminance

Luminous intensity and illuminance is measured in the candela (cd) and lux (lx). Conversions between SI and other units use exact, internationally agreed factors maintained by NIST.
→Source: NIST — International System of Units (SI)

International System of Units (SI)

Authoritative definitions for luminous intensity and illuminance, from the BIPM SI Brochure (9th edition), the defining reference for the SI.
→Source: BIPM — SI Brochure (9th ed.)

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