Free Online Illumination & Light Units Converter

Free Online Illumination & Light Units Conversion Tool

Our comprehensive Illumination and Light Units Converter is an essential tool for lighting designers, photographers, engineers, architects, and anyone working with light measurements. This powerful converter allows you to instantly convert between dozens of light measurement units including lumens, lux, candela, foot-candles, nits, lamberts, apostilbs, and many more. Whether you're designing lighting systems, setting up photography equipment, working on display technology, or studying optics, this tool provides accurate conversions with real-time results.

How to Use This Light Units Converter (Step-by-Step):

• Enter Value: Input the numerical light measurement value you want to convert in the "Light Value" field
• Select Source Unit: Choose the unit of your input value from the dropdown menu (e.g., lumens, lux, candela)
• View Results: Instantly see the converted values in all major light measurement units in the results panel
• Additional Actions: Use the buttons to copy results, swap units, or reset the converter for new calculations

Real-Life Application Examples:

For Lighting Design: Convert between lux and foot-candles when designing indoor or outdoor lighting systems. Office lighting typically requires 300-500 lux (28-46 foot-candles), while detailed work may need 750-1000 lux (70-93 foot-candles).

For Photography & Videography: Convert between different light measurement units when setting up studio lighting or calculating exposure. Understanding that 1000 lux equals approximately 93 foot-candles helps when working with light meters from different regions.

For Display Technology: Convert between nits and foot-lamberts when specifying display brightness. A typical computer monitor might be 200-300 nits (58-88 foot-lamberts), while HDR displays can reach 1000+ nits.

For Architecture & Construction: Convert between different illumination units when designing building lighting to meet international standards and regulations across different measurement systems.

Common Light Measurement Unit Definitions:

• Lumen (lm): SI unit of luminous flux - total quantity of visible light emitted by a source
• Lux (lx): SI unit of illuminance - luminous flux per unit area (lumens per square meter)
• Candela (cd): SI unit of luminous intensity - light power per unit solid angle
• Foot-candle (fc): Imperial unit of illuminance - lumens per square foot
• Nit (nt): SI unit of luminance - candelas per square meter (display brightness)
• Foot-lambert (fL): Imperial unit of luminance - based on foot-candle and surface reflectivity
• Lambert (L): CGS unit of luminance - named after Johann Heinrich Lambert
• Apostilb (asb): Non-SI unit of luminance - equivalent to 1/π candela per square meter

Who Should Use This Light Units Converter?

• Lighting Designers & Engineers: Essential for designing efficient and compliant lighting systems across different standards
• Photographers & Videographers: Perfect for understanding and converting light measurements for optimal exposure
• Display & Screen Manufacturers: Ideal for specifying and comparing display brightness across different units
• Architects & Interior Designers: Useful for meeting lighting requirements in building codes and design standards
• Students & Educators: Valuable for physics, engineering, and photography courses dealing with optics and light
• DIY Enthusiasts: Great for home lighting projects, grow lights, and custom lighting installations

Frequently Asked Questions

What's the difference between lumens, lux, and candela?
Lumens measure total light output, lux measures light falling on a surface (illuminance), and candela measures light intensity in a specific direction. Think of lumens as "total light," lux as "light per area," and candela as "brightness in a direction."

How are foot-candles related to lux?
1 foot-candle = 10.764 lux. This conversion comes from the relationship between square feet and square meters (1 ft² = 0.0929 m²). Foot-candles are commonly used in the US, while lux is used internationally.

What are nits used for?
Nits (candelas per square meter) are primarily used to measure the brightness of displays like monitors, TVs, smartphones, and digital signs. Higher nits values indicate brighter displays.

How accurate are the conversions?
Our converter uses precise conversion factors based on international standards. For most practical applications in lighting design, photography, and engineering, the accuracy is more than sufficient.

Can I convert between photometric and radiometric units?
This converter focuses on photometric units (light as perceived by human vision). Radiometric units (physical light energy) require different conversion factors based on wavelength and require knowledge of the light source spectrum.

Light Unit Conversion Factors Reference:

For quick reference, here are some key conversion factors:

• 1 lux = 0.0929 foot-candles
• 1 foot-candle = 10.764 lux
• 1 candela = 1 candlepower (approximately)
• 1 nit = 1 candela per square meter
• 1 foot-lambert = 3.426 candelas per square meter
• 1 lambert = 3183.1 candelas per square meter
• 1 apostilb = 0.3183 candelas per square meter
• 1 lumen = 1 candela × steradian (for isotropic source)

Typical Light Levels in Practice:

• Moonlight: 0.1-1 lux
• Residential Lighting: 50-300 lux
• Office Lighting: 300-500 lux
• Supermarket Lighting: 750-1000 lux
• Overcast Daylight: 1000-2000 lux
• Full Daylight (not direct sun): 10,000-25,000 lux
• Direct Sunlight: 32,000-100,000 lux

Common Light Source Luminous Efficacy:

• Incandescent Bulb: 10-17 lumens/watt
• Halogen Bulb: 15-25 lumens/watt
• Compact Fluorescent (CFL): 45-75 lumens/watt
• LED Bulb: 80-150 lumens/watt
• Professional LED: 150-200+ lumens/watt

Display Brightness Reference:

• Smartphone (indoor): 200-600 nits
• Computer Monitor: 200-350 nits
• HDR TV: 400-1500+ nits
• Outdoor Display: 1500-5000+ nits
• Sunlight-readable Display: 1000-2500+ nits