Illuminance Converter – Lux to Foot-Candles in 3 Easy Steps
Illuminance Converter
Use this illuminance converter: type a value into any field to instantly convert across all lighting intensity measurements.
Use this free illuminance converter to change lux to foot-candles and back, and to convert phot and nox, the less common illuminance units. Type a value into any box and the other three update instantly, with a reference chart of the key conversion factors.
Quick answer
1 foot-candle = 10.7639 lux, and 1 lux = 0.0929 foot-candles. To convert lux to foot-candles, divide by 10.7639. So 500 lux (a typical office) is 46.45 fc, and 50 fc is 538.2 lux. 1 phot = 10,000 lux and 1 lux = 1,000 nox.
Table of Contents
Lighting standards, light meters and lamp data sheets use different units. European and international guides use lux, while many US building codes and photographers still talk in foot-candles.
This illuminance converter keeps all four units in sync, so you can compare a spec sheet, a code requirement and a light meter reading without doing the maths by hand.
Illuminance Conversion Formulas
- Foot-candles = lux ÷ 10.7639
- Lux = foot-candles × 10.7639
- Phot = lux ÷ 10,000
- Nox = lux × 1,000
- 1 lux = 1 lumen per square metre; 1 foot-candle = 1 lumen per square foot.
Lux to Foot-Candles Chart
| Lux | Foot-candles | Typical setting |
|---|---|---|
| 50 | 4.65 | Corridors, stairs |
| 100 | 9.29 | Living rooms, warehouses |
| 300 | 27.87 | Classrooms, general offices |
| 500 | 46.45 | Desk work, reading |
| 750 | 69.68 | Detailed drawing, workshops |
| 1,000 | 92.90 | Precision work, operating areas |
| 10,000 | 929.03 | Full daylight, not direct sun |
| 100,000 | 9,290.31 | Direct sunlight |
How to Use the Illuminance Converter
Step 1: Enter a Value in Lux
Type the light level in Lux (lx). For 500 lux, the converter shows 46.45 foot-candles, 0.05 phot and 500,000 nox.
Step 2: Convert Foot-Candles to Lux
Type in Foot-Candles (fc) to go the other way. A US code requirement of 50 fc equals 538.2 lux. All other fields update at the same time.
Step 3: Check the Reference Matrix
The Base Conversion Reference Matrix shows the four key factors: 1 fc = 10.7639 lx, 1 ph = 10,000 lx, 1 lx = 0.0929 fc and 1 lx = 1,000 nx. Press Clear Fields to start again.
Lux vs Lumens
Lumens measure the total light a lamp gives out. Lux measures how much of that light lands on a surface. A 1,000 lumen bulb spread over 1 square metre gives 1,000 lux, but spread over 10 square metres it gives only 100 lux. That is why the same lamp feels bright in a closet and dim in a hall.
Recommended Light Levels
- Homes: 100–300 lux for living areas, 300–500 lux for kitchens and reading.
- Offices: 300–500 lux for general work.
- Retail: 500–1,000 lux depending on display needs.
- Plant growing: often measured in lux or foot-candles, with many leafy plants needing several thousand lux.
Lux and Foot-Candles in Photography and Film
Cinematographers and photographers often use foot-candles because classic light meters and lighting tables were built around them. A key light of 100 fc (about 1,076 lux) is a common starting point for a studio interview, while bright outdoor shade can easily reach 1,000 fc. Use the illuminance converter to match a lighting plan written in one unit with a meter that reads in the other.
Why Light Falls Off With Distance
Illuminance follows the inverse square law: double the distance from a small light source and the lux on the surface drops to about a quarter. Moving a desk lamp from 50 cm to 1 m away can cut the light on your page from 800 lux to around 200 lux, even though the lamp itself has not changed.
Measuring Light Levels
A light meter or a phone light-meter app measures lux at the sensor. Hold it flat at desk or floor height, pointing up, and take several readings around the room. Convert the average with the illuminance converter if your standard uses foot-candles.
More unit tools: the Sound Level Converter, the Screen DPI PPI Converter and the Frequency Converter.
Frequently Asked Questions
How many lux is one foot-candle?
One foot-candle equals 10.7639 lux.
How do I convert lux to foot-candles?
Divide lux by 10.7639. 500 lux ÷ 10.7639 = 46.45 fc.
What is a phot?
A phot is an old CGS unit of illuminance equal to 10,000 lux.
What is a nox?
A nox is one thousandth of a lux, used for very low night-time light levels.
How many lux do I need for an office?
About 300–500 lux is typical for general office work.
Is my data stored?
No. The illuminance converter runs in your browser and nothing is saved.