Illumination Converter
ScienceConvert illuminance units including lux, foot-candles, and lumens/m². Essential for photography, lighting design, and architectural light level specifications.
From
To
All conversionsfor 1 Lux (lx)
| Lux (lx) | 1 |
| Millilux (mlx) | 1000 |
| Kilolux (klx) | 0.001 |
| Megalux (Mlx) | 0.000001 |
| Foot-candle (fc) | 0.092903044 |
| Phot (ph) | 0.0001 |
| Lumen per Square Inch (lm/in²) | 0.00064516004 |
What is a Illumination?
An Illumination Converter converts between units of illuminance — the measurement of how much luminous flux (light) falls on a surface per unit area. Illuminance tells you how brightly a surface is lit, which is fundamental to lighting design, photography, workplace safety standards, and architectural specifications.
The SI unit for illuminance is the lux (lx), defined as one lumen per square metre (lm/m²). The US customary equivalent is the foot-candle (fc), equal to one lumen per square foot. This converter also covers the historical CGS unit phot (10,000 lux), lumen per square inch (used in display panel specs), and SI prefix variants (millilux, kilolux, megalux) for measuring everything from starlight to direct sunlight.
For Indian professionals, illuminance conversion is most often needed when working with US-specification equipment. Film lights, studio luminaires, and projectors imported from the US are frequently rated in foot-candles, while BIS standards (IS 3646 for interior lighting, IS 1944 for road lighting) specify lux. A lighting designer specifying a 1000 lux work surface for an office in Mumbai must know that this equals 92.9 foot-candles when selecting from a US product catalogue.
Illuminance is distinct from luminance — use this converter for how much light falls on a surface, not for how bright a surface appears to an observer. The Energy Converter is useful alongside this when calculating the energy efficiency of lighting systems (lumens per watt).
How to use this Illumination calculator
- The converter loads with Lux as the FROM unit and Foot-candle as the TO unit — the most common conversion for Indian professionals working with US equipment.
- Select your source unit from the FROM dropdown. Choose from SI (Lux, Millilux, Kilolux, Megalux), US Customary (Foot-candle, Lumen/in²), or CGS (Phot).
- Enter your illuminance value in the input field. The result updates immediately as you type.
- Select your target unit from the TO dropdown.
- Use the ⇅ swap button to instantly reverse the FROM and TO units — useful when converting from foot-candles back to lux.
- Scroll down to the reference table to see your value in all 7 units at once — useful for writing multi-standard specifications.
- Compare the result against the BIS IS 3646 requirements for your space type to confirm compliance before finalising your lighting design.
Formula & Methodology
This is a linear converter using the lux (lx) as the common base unit. All conversions follow:Result = Input × (toBase_from ÷ toBase_to)Key toBase values (lux): | Unit | Lux equivalent | |---|---| | Lux (lx) | 1 | | Millilux (mlx) | 0.001 | | Kilolux (klx) | 1,000 | | Megalux (Mlx) | 1,000,000 | | Foot-candle (fc) | 10.76391 | | Phot (ph) | 10,000 | | Lumen per Square Inch (lm/in²) | 1,550.003 | Derivation of key factors: - 1 foot-candle = 1 lm/ft² = 1 lm / (0.3048 m)² = 1 / 0.09290304 lux = 10.76391042 lux (exact, from the international foot definition of 0.3048 m) - 1 phot = 1 lm/cm² = 1 lm / 0.0001 m² = 10,000 lux (exact) - 1 lm/in² = 1 lm / (0.0254 m)² = 1 / 0.00064516 = 1550.0031 lux (exact, from 1 inch = 0.0254 m) Worked example — studio lighting in Chennai: A broadcast studio in Chennai requires 1200 lux on the presenter desk (per channel specification). The production designer is selecting from a US product catalogue rated in foot-candles.1200 lux × (1 ÷ 10.76391) = 111.5 foot-candlesAny fixture delivering at least 112 foot-candles at the working distance meets the spec. Factor in a maintenance coefficient of 0.8 for lamp ageing, so specify 140 foot-candles at new-lamp output to ensure compliance over the fixture's service life. Common reference conversions: | Lux | Foot-candles | Phot | Kilolux | |---|---|---|---| | 100 | 9.29 | 0.01 | 0.1 | | 500 | 46.45 | 0.05 | 0.5 | | 1000 | 92.90 | 0.1 | 1.0 | | 10,000 | 929.0 | 1.0 | 10.0 |
Frequently Asked Questions
What is illuminance and how is it measured?
Illuminance is the measure of how much luminous flux (light) falls on a surface per unit area. It quantifies how brightly a surface is lit, not how bright the light source itself is. The SI unit for illuminance is the lux (lx), equal to one lumen per square metre (lm/m²). The higher the lux value, the more light is reaching the surface.
What is the difference between lux and foot-candle?
Lux and foot-candle both measure illuminance, but use different area bases. One lux equals one lumen per square metre, while one foot-candle equals one lumen per square foot. Since one square foot equals 0.0929 m², one foot-candle equals approximately 10.764 lux. Lux is the international SI standard used in India and most of the world; foot-candle is used primarily in the United States for film, television, and theatrical lighting specifications.
What is a lux in practical terms?
A single lux is a very low level of light — roughly equivalent to a full moon on a clear night (about 1 lux). A well-lit office has 300–500 lux; outdoor sunlight on a clear day measures 32,000–100,000 lux; a TV studio is lit to around 1000–2000 lux for broadcast; and direct midday sun can reach 1 megalux (1,000,000 lux). These reference points help calibrate your expectations when reading light metre or datasheet values.
What illuminance levels does India's BIS require for workplaces?
The Bureau of Indian Standards (BIS) specifies illuminance requirements for workplaces under IS 3646 (Code of Practice for Interior Illumination). General office work requires 300–500 lux; drawing and design offices need 750 lux; hospital operating theatres require 10,000–20,000 lux; and fine assembly work in manufacturing needs 1500–3000 lux. These are measured at the working plane using a calibrated lux metre. For outdoor spaces, BIS specifies road lighting levels in lux under IS 1944.
How do I convert lux to foot-candles?
To convert lux to foot-candles, divide by 10.764. For example, 500 lux ÷ 10.764 = 46.45 foot-candles. To convert foot-candles to lux, multiply by 10.764: 50 foot-candles × 10.764 = 538.2 lux. This conversion is frequently needed when comparing US film and TV lighting standards (specified in foot-candles) with international and BIS standards (specified in lux).
What is a phot and when is it used?
A phot (ph) is a CGS unit of illuminance equal to one lumen per square centimetre, which equals 10,000 lux. It is not part of the SI system and is rarely used in modern practice, but appears in older technical literature and historical physics texts. One phot represents an extremely high illuminance level — roughly equivalent to bright sunlight focussed onto a small area.
How do I use the Illumination Converter?
Select your source unit from the FROM dropdown — for example, Lux. Enter the illuminance value in the input field. Select your target unit from the TO dropdown — for example, Foot-candle. The result appears immediately. Use the ⇅ swap button to reverse the conversion direction, and scroll to the reference table to see your value simultaneously in all available units.
What is the illuminance required for photography studios?
Photography studio lighting requirements vary by subject and style. Portrait photography typically uses 500–1000 lux at the subject plane for available-light setups, while strobe-based studios are often specified in guide numbers or watt-seconds rather than lux. Continuous lighting for video work in India is commonly specified in foot-candles for US-origin equipment: a typical 3-light interview setup delivers 50–100 foot-candles (540–1080 lux) on the subject. Indian broadcast studios following Doordarshan and private channel specifications typically require 800–1200 lux.
What is the difference between illuminance and luminance?
Illuminance (measured in lux) describes how much light arrives at a surface — the incoming light. Luminance (measured in candela per square metre, cd/m²) describes how much light leaves a surface toward the observer — the outgoing or reflected light. A dark wall in a brightly lit room has high illuminance but low luminance; a self-luminous screen like a monitor has luminance regardless of incoming light. These are different physical quantities and cannot be directly converted between each other.
How many lux is adequate for outdoor sports venues in India?
Indian sports facility lighting follows BCCI and international federation standards depending on the sport. A club-level cricket ground requires 200–300 lux; a stadium hosting televised matches needs 1500–2000 lux for HD broadcast and 2500+ lux for 4K broadcast. Football pitches for FIFA-sanctioned matches require a minimum of 1400 lux at the playing surface. Badminton courts in BIS-compliant facilities need 300–500 lux for recreational play and 1000–1500 lux for national competition.
What is lumen per square inch used for?
Lumen per square inch (lm/in²) appears in specifications for display panels, projector outputs, and flat-panel lighting modules — particularly in US-origin datasheets for LED backlights and industrial monitors. One lm/in² equals 1550.003 lux, making it a very high-intensity unit used for small, intense light sources rather than room-scale illumination. When an Indian engineer receives a projector or panel spec in lm/in², this converter instantly gives the lux equivalent for comparison with BIS and room illumination standards.
What is the formula for illuminance conversion?
All illuminance units in this converter are linear — they convert through a common base unit (lux) using: Result = Input × (toBase_from ÷ toBase_to). For example, to convert 200 foot-candles to lux: 200 × 10.76391 ÷ 1 = 2152.78 lux. To convert 5000 lux to phot: 5000 × 1 ÷ 10000 = 0.5 phot. The conversion factor between foot-candle and lux (10.76391) is derived from the exact definition of 1 foot = 0.3048 metres.