Illumination Converter

What Is Illumination?

Illumination, more precisely termed illuminance, measures how much luminous flux actually falls on a given surface area. Where luminous intensity describes a source's directional output and luminous flux describes its total output, illuminance answers the practical question every lighting designer, photographer, and safety officer actually cares about: how bright is it here, on this desk, this factory floor, or this camera sensor?

Our Illumination Converter works with the SI unit lux (lx), equal to one lumen per square meter, across its full metric prefix range, giving lighting professionals in the US, UK, and worldwide an instant way to translate between millilux, lux, and kilolux readings from light meters and design specifications.

Lux and the US Customary Foot-candle

While the lux dominates international lighting standards, the United States has long used the foot-candle (fc), defined as one lumen per square foot. The conversion between the two is exact and derives directly from the definition of the foot: since one foot equals 0.3048 meters, one foot-candle equals precisely 10.7639 lux. American lighting designers, architects, and OSHA compliance officers still routinely specify illuminance in foot-candles even as manufacturers increasingly report light meter readings in lux, making fluent conversion between the two units an everyday necessity on both sides of the Atlantic.

Real-World Illuminance Levels

Illuminance spans an astonishing range in everyday life. A moonlit night produces roughly 0.1 to 1 lux, barely enough to navigate by. A well-lit office, per both US IES (Illuminating Engineering Society) recommendations and the UK's BS EN 12464-1 workplace lighting standard, targets between 300 and 500 lux for general tasks. An overcast day outdoors can reach 1,000 lux, while direct summer sunlight can exceed 100,000 lux — a hundred-thousand-fold range that makes the prefix ladder (millilux through kilolux) genuinely essential for practical specification work rather than a mere mathematical curiosity.

Workplace Lighting Standards

Both American and British regulatory frameworks set minimum illuminance requirements to protect worker safety and productivity. OSHA's general industry guidelines specify minimums ranging from 5 foot-candles in warehouses to 100 foot-candles in fine assembly work, while the UK's Health and Safety Executive references BS EN 12464-1 for task-specific lux targets — typically 500 lux for general office work and up to 1,500 lux for detailed inspection tasks. Facility managers and lighting engineers routinely need to convert between the lux-based European specifications and foot-candle-based American light meters when auditing multinational facilities or importing lighting fixtures rated in a different regional standard.

Photography and Exposure

Illuminance also underpins photographic exposure calculations. Cinematographers and photographers use handheld lux meters (or incident light meters calibrated in foot-candles) to determine correct exposure settings before a shoot, particularly in controlled studio environments where consistent lighting across multiple takes is critical. Understanding that a typical studio key light might sit around 1,000 to 2,000 lux, while a dimly lit interior scene might be closer to 50 lux, allows cinematographers to plan lighting rigs with the same numerical precision that architects apply to building interiors.

Horticultural and Agricultural Lighting

Illuminance measurement has also become central to indoor and greenhouse horticulture, an increasingly significant industry across both the US and UK as controlled-environment agriculture expands. Growers use lux meters, alongside more specialized photosynthetically active radiation sensors, to verify that supplemental grow lighting delivers sufficient illuminance for healthy plant development, with target ranges varying enormously by crop — leafy greens typically thrive around 10,000 to 20,000 lux, while fruiting crops such as tomatoes often require considerably more. Getting these lux targets right, and being able to convert confidently between meter readings and manufacturer specifications, directly affects crop yield, energy costs, and the economic viability of indoor growing operations.