How to Use This Tool
Choose a Category
Select Luminous Intensity, Luminous Flux, or Illuminance using the buttons at the top. Each category has its own set of units.
Enter a Value
Type the value you want to convert into the input field. Decimals and scientific notation are supported.
Choose Your Units
Pick a From unit and a To unit from the dropdowns. Use the swap button to flip them instantly.
Read the Result
The converted value appears instantly below the inputs. Click Copy to put it on your clipboard.
Frequently Asked Questions
Is this tool really free?
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Yes, completely free with no limits and no sign-up. Everything runs in your browser.
Is my data sent to a server?
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No. All conversion math happens directly in your browser. Nothing you type is ever sent anywhere.
What are the three categories?
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Luminous Intensity measures how bright a light source appears in a given direction (candela). Luminous Flux measures the total light output of a source (lumens). Illuminance measures how much light hits a surface (lux).
Can I convert between categories?
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No. Intensity, flux, and illuminance are different physical quantities. You can only convert between units within the same category.
What is a Lux?
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Lux is the standard unit of illuminance. One lux equals one lumen per square meter. It measures how much light reaches a surface.
What is a Candela?
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Candela is the standard unit of luminous intensity. It measures the brightness of a light source in a specific direction.
What is a Lumen?
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Lumen is the standard unit of luminous flux. It measures the total amount of visible light emitted by a source in all directions.
What is a Foot-candle?
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A foot-candle is one lumen per square foot. It is the US equivalent of lux and is commonly used in lighting design and photography in the United States.
What is a Phot?
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A phot equals 10,000 lux. It is an older unit from the CGS system, occasionally found in older lighting references.
Does it update instantly?
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Yes. All results recalculate as soon as you change any input or switch categories.
What Is Luminosity Converter?
Luminosity Converter is a free tool that converts between 13 light measurement units across three categories right in your browser. Choose Luminous Intensity (candela, candlepower, hefnerkerze), Luminous Flux (lumens), or Illuminance (lux, foot-candle, phot, nox) and convert within that category. Nothing you type is ever sent anywhere - all math runs locally on your device.
Switch between categories using the buttons at the top. Each category has its own set of units, and the result updates live as you type.
Features Explained
Three Light Categories
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Switch between Luminous Intensity, Luminous Flux, and Illuminance using the buttons at the top. Each category has its own units.
Luminous Intensity Units
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Candela, Millicandela, Kilocandela, Lumen per Steradian, Candlepower, and Hefnerkerze for measuring how bright a source appears in a given direction.
Luminous Flux Units
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Lumen, Millilumen, and Kilolumen for measuring the total visible light output of a source.
Illuminance Units
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Lux, Foot-candle, Phot, and Nox for measuring how much light reaches a surface.
Category Separation
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Conversions happen within the same category only, because intensity, flux, and illuminance are different physical quantities.
Historical Units
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Candlepower and Hefnerkerze are older units still found in vintage specifications and historical documents.
Instant Conversion
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The result updates live as you type. No Convert button needed.
Swap Button
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Click the swap button between the From and To dropdowns to flip them instantly.
Copy to Clipboard
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Click Copy to put the converted value on your clipboard in one click.
100% Browser-Based
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All conversion math runs directly in your browser. Nothing you type is ever sent to any server.
Who Is This Tool For?
Lighting Designers
Convert between lux, foot-candles, and lumens when designing indoor and outdoor lighting layouts.
Photographers
Convert between lux and foot-candles to understand light levels and set exposure correctly.
Cinematographers
Convert illuminance values between foot-candles and lux for set lighting and exposure planning.
Architects
Convert lighting specifications between lux and foot-candles for building design and compliance.
Electrical Engineers
Convert between candela, lumens, and lux for luminaire design and photometric calculations.
Students
Convert between light units for physics and optics homework.
Teachers
Demonstrate the difference between intensity, flux, and illuminance during science lessons.
Interior Designers
Convert light level recommendations between lux and foot-candles for room designs.
Safety Officers
Verify workplace illumination meets standards by converting between lux and foot-candles.
Stage Lighting Technicians
Convert between candela and lumens when selecting and positioning stage lights.
Museum Curators
Convert illuminance values to protect light-sensitive artworks while meeting visibility standards.
Horticulturists
Convert grow light output between lumens and lux for plant lighting calculations.
Facility Managers
Convert lighting audit measurements between lux and foot-candles for energy compliance.
Optometrists
Convert examination room light levels between lux and foot-candles.
Automotive Engineers
Convert headlight and dashboard light intensity between candela and millicandela.
LED Manufacturers
Convert product specifications between lumens, candela, and lux for datasheets.
Energy Auditors
Convert measured illuminance values between units for efficiency reports.
Film Set Designers
Convert light level requirements between foot-candles and lux from different lighting guides.
Sports Facility Managers
Convert field and court illumination standards between lux and foot-candles.
Security Consultants
Verify that surveillance lighting meets minimum lux or foot-candle requirements.
Astronomers
Convert stellar luminosity measurements between historical and modern units.
Researchers
Convert between SI and traditional light units for cross-referencing publications.
Hobbyists
Explore light measurement units for photography, aquariums, or home lighting projects.
Anyone
Quickly convert any light measurement between 13 units across three categories.
Tips for Best Results
Pick the right category first
Choose Intensity for source brightness, Flux for total light output, or Illuminance for light on a surface. You cannot convert across categories.
Lux vs foot-candle
1 foot-candle = about 10.76 lux. Foot-candles are used in the US; lux is used everywhere else. The tool converts between them instantly.
Common lux levels
Office: 300-500 lux. Living room: 100-300 lux. Outdoor overcast: 1,000 lux. Direct sunlight: 100,000 lux.
Lumens for bulb shopping
A traditional 60-watt incandescent bulb produces about 800 lumens. Use lumens (flux) to compare brightness across bulb types.
Candela for focused beams
Candela measures intensity in one direction. A spotlight with high candela is very bright in a narrow beam.
Foot-candle for US standards
US building codes and workplace safety standards often specify light levels in foot-candles.
Nox for very low light
A nox is 0.001 lux. It is used for measuring very low light levels like moonlight and nighttime conditions.
Use the swap button
Click the swap button between the dropdowns to flip From and To instantly.
Copy the result
Click Copy next to the result to put the value on your clipboard.
Privacy is built in
Nothing you type is ever sent to any server. All math runs in your browser.
Privacy & Security
This tool runs 100% in your browser. Your files stay entirely on your own device. Nothing is uploaded, nothing is shared, and no server, advertiser, or third party has access to your files.
If a tool saves your work on your own device, you can remove it at any time using the Clear All button. Some tools rely on an external service to return their result; in those cases, only the minimum data required for the request is sent, and never your files or content. Any ads shown on this page run in an isolated frame and cannot read, touch, or transmit anything you upload, paste, type, or download here. Advertisers may see standard visit information like your IP address and which page you're on, as described in our Privacy Policy, but your data itself stays fully under your control.
