# Luminosity / Light Converter

Free light unit converter. Convert between lux, foot-candles, phot, lumens, and candela for illuminance, luminous flux, and intensity measurements.

## What this calculates

Convert between common light measurement units including lux, foot-candles, phot, lumens, and candela. Covers illuminance, luminous flux, and luminous intensity conversions.

## Inputs

- **Value** — min 0
- **Measurement Type** — options: Illuminance (lux, fc), Luminous Flux (lumens), Luminous Intensity (candela)
- **From** — options: Lux (lx), Foot-candle (fc), Phot (ph), Nox, Lumen (lm), Candela (cd), Candlepower (cp)
- **To** — options: Lux (lx), Foot-candle (fc), Phot (ph), Nox, Lumen (lm), Candela (cd), Candlepower (cp)

## Outputs

- **Result** — The converted light measurement value.
- **Conversion** — formatted as text — Conversion explanation and notes.

## Details

Light measurement involves several related but distinct quantities. Understanding the differences is key to proper conversion.

Light Measurement Types

- Illuminance (light hitting a surface): measured in lux (lm/m²) or foot-candles (lm/ft²)

- Luminous flux (total light output): measured in lumens (lm)

- Luminous intensity (light in a direction): measured in candela (cd)

Key Conversion Factors

- 1 foot-candle = 10.764 lux

- 1 phot = 10,000 lux

- 1 nox = 0.001 lux (used for very dim light)

Typical Illuminance Levels

- Full daylight: 10,000-25,000 lux

- Office lighting: 300-500 lux

- Living room: 50-200 lux

- Full moonlight: 0.05-0.3 lux

- Starlight: 0.0002-0.001 lux

## Frequently Asked Questions

**Q: How do I convert lux to foot-candles?**

A: Divide the lux value by 10.764. For example, 500 lux = 500 / 10.764 = 46.45 foot-candles. One foot-candle is the illuminance of one lumen per square foot, while one lux is one lumen per square meter.

**Q: What is the difference between lumens and lux?**

A: Lumens measure total light output (luminous flux) from a source, while lux measures how much light falls on a surface (illuminance). A 1,000-lumen bulb produces the same total light whether in a small or large room, but the lux at any surface depends on distance and room size.

**Q: Can I convert lumens to lux directly?**

A: Not without knowing the area. Lux = lumens / area (in m²). For a point source, lux = candela / distance² (in meters). This converter handles within-category conversions; cross-category conversion requires geometric information.

**Q: How many lumens do I need for a room?**

A: General guidelines: living rooms need 1,500-3,000 lumens, kitchens need 3,000-4,000 lumens, bedrooms need 1,000-2,000 lumens, and offices need 3,000-6,000 lumens. The exact amount depends on room size, ceiling height, and wall color.

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Source: https://vastcalc.com/calculators/conversion/luminosity-converter
Category: Conversion
Last updated: 2026-04-21