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Illuminance Converter

Lux • Foot-candles • lm/m² • phot

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How to Use the Illuminance Converter

Enter a value — a positive light level reading.
Select From unit — lux, foot-candles, kilolux, and more.
Select To unit — the unit you want the answer in.
Read the result — plus a grid in lux, foot-candles, kilolux and lm/ft², and a real-world brightness label.
Use swap (⇄) — flip the conversion direction instantly.

Why Use This Illuminance Converter

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Exact 10.764 Factor

1 foot-candle = 10.7639 lux exactly (lumens per square foot vs per square meter). No rounding guesswork.

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Photography & Plants

Built for camera light readings, workspace lighting standards, and indoor plant / grow-light targets.

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100% Private

All conversions run in your browser — no server, no account, nothing sent anywhere.

Illuminance Guide — Lux, Foot-candles & Light Levels

Illuminance is the amount of light falling on a surface, measured as luminous flux (lumens) per unit area. The SI unit is the lux (1 lux = 1 lumen per square meter). The US customary unit is the foot-candle (1 fc = 1 lumen per square foot). Because a square meter is larger than a square foot, the same light spread over a square meter is more diluted — so 1 foot-candle equals 10.7639 lux.

The core conversion: to convert foot-candles to lux, multiply by 10.764. To convert lux to foot-candles, divide by 10.764 (or multiply by 0.0929). Examples: an office lit to 500 lux is about 46 foot-candles; a 50 fc workshop is about 538 lux. Lighting designers in the US often specify foot-candles, while the rest of the world and most light meters use lux — making this conversion a daily need for photographers, architects, and facility managers.

Don't confuse illuminance with lumens. Lumens measure the total light output of a bulb (luminous flux), while lux and foot-candles measure how much of that light actually reaches a surface — which depends on distance and beam spread. A 800-lumen bulb produces very different lux at 1 meter versus 3 meters away. For plants, "lux" is a rough proxy; serious growers use PPFD (µmol/m²/s), but lux targets remain a useful everyday guide.

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Natural Light

Direct sunlight: 32,000–100,000 lux. Overcast day: 1,000–10,000 lux. Sunrise/sunset: ~400 lux. Full moon: ~0.25 lux. Twilight: ~10 lux. Deep dusk: ~1 lux.

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Indoor Standards

Office work: 300–500 lux. Detailed/drafting: 750–1,000 lux. Living room: 100–300 lux. Kitchen counter: 300–500 lux. Supermarket: 750–1,000 lux. Hospital exam: 1,000 lux.

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Plants & Grow

Low-light houseplants: 1,000–2,500 lux. Medium: 2,500–10,000 lux. High-light/flowering: 10,000–50,000 lux. Seedlings: ~5,000–10,000 lux. Most plants want 12–16 hr/day.

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The Conversions

1 fc = 10.764 lux. 1 lux = 0.0929 fc. 1 klx = 1,000 lux. 1 phot = 10,000 lux (lm/cm²). 1 nox = 0.001 lux. lm/m² = lux; lm/ft² = foot-candle.

Illuminance Conversion FAQ

How do I convert lux to foot-candles? ▾

Divide lux by 10.764 (or multiply by 0.0929). For example, 500 lux ÷ 10.764 = 46.5 foot-candles, and 1,000 lux = 92.9 fc. To go the other way, multiply foot-candles by 10.764: a 50 fc reading equals 538 lux. The factor comes from the area difference — 1 square meter = 10.7639 square feet.

What is the difference between lux and lumens? ▾

Lumens measure the total light a source emits in all directions (luminous flux). Lux measures how much of that light lands on a surface (illuminance = lumens per square meter). The same 800-lumen bulb produces high lux close up and low lux far away, because the light spreads out. So lumens describe the bulb; lux describes the lighting at a specific spot. This converter handles illuminance units (lux, foot-candles), not raw lumen output.

How many lux do office workers need? ▾

General office work typically calls for 300–500 lux (about 28–46 foot-candles). Tasks requiring fine detail — drafting, inspection, detailed assembly — need 750–1,000 lux (70–93 fc). Hallways and low-activity areas can be 100–200 lux. These are illuminance levels measured at the work surface, and many lighting codes and the IES recommend values in this range.

How much light is direct sunlight in lux? ▾

Direct midday sunlight is roughly 32,000 to 100,000 lux depending on season, latitude, and atmospheric conditions. A bright overcast day is 1,000–10,000 lux, and full daylight in shade is around 10,000–25,000 lux. For comparison, a well-lit office is only 300–500 lux — outdoor light is dramatically brighter than indoor lighting, which is why cameras and plants behave so differently inside.

Can I use lux to measure light for plants? ▾

Lux is a useful rough guide for plant lighting, but it's not ideal because it's weighted to human eye sensitivity, not plant photosynthesis. Low-light houseplants do well around 1,000–2,500 lux, medium-light plants want 2,500–10,000 lux, and high-light or flowering plants need 10,000–50,000 lux. For precise horticulture, growers use PPFD (µmol/m²/s) instead, but lux targets remain a practical everyday reference.