Illuminance Converter

Amaze SEO Tools offers a free Illuminance Converter that takes an illuminance value in one unit and converts it to all other supported illuminance units simultaneously — eliminating the need for manual conversion formulas and lookup tables.

Illuminance measures how much luminous flux (visible light) falls on a given surface area. It answers the practical question: "How brightly lit is this surface?" This is fundamentally different from luminous intensity (how bright a light source is) or luminance (how bright a surface appears to the eye). Illuminance is what you measure when you check whether an office has adequate lighting, whether a photography set is properly lit, or whether a road meets minimum safety standards after dark.

The challenge is that different industries, regions, and applications use different illuminance units. Architects and lighting designers in most of the world work in lux, while those in North America frequently encounter foot-candles. Scientists may use phots or lumens per square centimeter, and specialized low-light applications use nox or microlux. Our converter bridges all these systems: enter a value, select your source unit, click Convert, and see the equivalent in every other unit instantly.

Interface Overview

Value

The first input field is labeled "Value" — a single-line text field where you enter the numeric illuminance measurement you want to convert. Type any positive number, including decimals (e.g., 500, 32.5, 0.001). This is the illuminance quantity that will be converted from your selected source unit to all other units.

Convert From Lux to Others

Below the value field, a dropdown menu labeled "Convert From Lux to Others" lets you select the source unit for your conversion. The dropdown contains 9 illuminance units:

• Microlux (µlx) — One millionth of a lux. Used for extremely low-light measurements such as starlight, deep-sky astronomy, and nocturnal ecology studies.
• Millilux (mlx) — One thousandth of a lux. Used for measuring very dim lighting conditions such as moonless night skies, dark-adapted vision research, and sensitive photometric calibrations.
• Lux (lx) — The SI standard unit of illuminance. Equals one lumen per square meter (1 lm/m²). The most widely used illuminance unit globally for lighting design, building codes, workplace regulations, and general photometry.
• Kilolux (klx) — One thousand lux. Used for expressing high illuminance levels compactly, such as direct sunlight (approximately 100 klx) or intense industrial lighting.
• Lumen per square meter (lm/m²) — Numerically identical to lux (1 lx = 1 lm/m²). Expresses illuminance explicitly in terms of luminous flux per unit area, which is useful in technical documentation where the relationship between lumens and area needs to be clear.
• Lumen per square centimeter (lm/cm²) — Illuminance expressed per square centimeter rather than per square meter. Since 1 m² = 10,000 cm², this unit is 10,000 times larger than lux. Equivalent to the phot. Used in some scientific and optical engineering contexts.
• Foot-candle (fc) — One lumen per square foot. The traditional illuminance unit in the United States and Canada, widely used in architectural lighting design, building codes, IESNA standards, and commercial lighting specifications. 1 foot-candle ≈ 10.764 lux.
• Phot (ph) — A CGS unit equal to one lumen per square centimeter (10,000 lux). Used in older scientific literature and some specialized optical applications. Named after the Greek word for light.
• Nox — A unit equal to one millilux (0.001 lux). Specifically designed for measuring very low illuminance levels in nighttime environments, nocturnal research, and dark-sky studies.

Select the unit your original value is expressed in. The default selection is Lux (lx), which is the SI standard unit for illuminance.

reCAPTCHA (I'm not a robot)

A verification checkbox sits below the dropdown. Tick "I'm not a robot" to confirm you are a human user before running the conversion.

Action Buttons

Three buttons appear beneath the reCAPTCHA:

Convert (Blue Button)

The primary action. After entering a value, selecting your source unit, and completing the reCAPTCHA, click "Convert" to calculate the equivalent illuminance in all other supported units. The results display below, showing every conversion at once.

Sample (Green Button)

Fills the value field with a pre-set example number and selects a default unit so you can see the converter in action before entering your own data. Helpful for understanding the output format.

Reset (Red Button)

Clears the value field, resets the dropdown to its default selection, and removes any displayed results — returning the tool to its original state.

How to Use Illuminance Converter – Step by Step

1. Open the Illuminance Converter on the Amaze SEO Tools website.
2. Enter your illuminance value in the "Value" field — type the numeric measurement you want to convert.
3. Select the source unit from the dropdown — choose the unit your value is currently expressed in (e.g., lux, foot-candle, phot).
4. Check the reCAPTCHA to verify you're not a bot.
5. Click "Convert" to see the equivalent illuminance in all other supported units.
6. Find and copy the values you need from the results list.

What Is Illuminance?

Illuminance is a photometric quantity that measures the total luminous flux (visible light energy) incident on a surface per unit area. In simple terms, it measures how much light is landing on a surface — not how much light a source emits, but how brightly a receiving surface is illuminated.

The fundamental formula is:

E = Φ / A

Where E is illuminance, Φ (phi) is the luminous flux in lumens, and A is the area of the surface in square meters (for lux) or square feet (for foot-candles).

Illuminance is distinct from related photometric quantities:

• Luminous intensity (candela) — Measures the brightness of a light source in a specific direction. Describes the source, not the surface.
• Luminous flux (lumen) — Measures the total amount of visible light emitted by a source in all directions. Describes total light output.
• Luminance (cd/m²) — Measures the brightness of a surface as perceived by the human eye. Depends on both incident light and surface reflectance.
• Illuminance (lux or foot-candle) — Measures light arriving at a surface. Depends on the light source's output, distance, and angle, but is independent of surface properties.

Conversion Reference Table

Typical Illuminance Levels

Understanding real-world illuminance levels helps put your measurements and conversions in context:

Where Is Illuminance Conversion Used?

• Architectural lighting design — Lighting designers specify illuminance levels for every room and surface in a building. International standards use lux while North American standards (IESNA) use foot-candles. Converting between these units is routine when working with international clients, multi-regional building codes, or luminaire specification sheets from different manufacturers.
• Workplace health and safety — Occupational safety regulations specify minimum illuminance levels for workplaces. European standards (EN 12464-1) are in lux; OSHA and IESNA guidelines in the U.S. use foot-candles. Compliance verification often requires converting measurements between these systems.
• Photography and cinematography — Photographers and videographers use light meters that may display readings in lux, foot-candles, or EV (exposure value). Converting between illuminance units helps when following lighting guides written in different unit systems or when matching equipment calibrated in different standards.
• Horticulture and grow lighting — Indoor growing operations measure light levels at the plant canopy in lux or foot-candles to ensure optimal photosynthesis rates. Different plant species have specific illuminance requirements, and grow light manufacturers may specify output in either unit system.
• Astronomy and nocturnal research — Measuring extremely low light levels — starlight, moonlight, artificial sky glow — requires units like microlux, millilux, or nox. Dark-sky preservation initiatives and light pollution studies use these units to quantify nighttime illuminance conditions.
• Museum and gallery lighting — Artworks, textiles, and historical artifacts have strict maximum illuminance limits to prevent light damage. Conservation standards specify these limits in lux (typically 50-200 lx depending on the material), and curators must verify that lighting installations comply.
• Road and outdoor lighting standards — Traffic safety regulations specify minimum illuminance levels for roads, intersections, parking lots, and pedestrian areas. These standards vary by region and use either lux or foot-candles, requiring conversion when applying international road lighting guidelines locally.
• Scientific research and optical engineering — Laboratory photometric measurements may use CGS units (phot, lumen per square centimeter) or SI units (lux). Converting between these is necessary when comparing data across different publication standards or calibration systems.

Lux vs Foot-Candle: The Most Common Conversion

The conversion between lux and foot-candles is by far the most frequently needed illuminance conversion, driven by the divide between metric and imperial measurement systems:

• 1 foot-candle = 10.764 lux (approximately 10.76 lux)
• 1 lux = 0.09290 foot-candles (approximately 0.093 fc)

The foot-candle is defined as one lumen per square foot, while lux is one lumen per square meter. Since 1 square meter = 10.764 square feet, the same luminous flux spread over one square foot produces 10.764 times the illuminance compared to one square meter — hence the conversion factor.

Quick mental shortcut: To roughly convert lux to foot-candles, divide by 10. To convert foot-candles to lux, multiply by 10. This approximation is within 8% of the exact value and is sufficient for most quick estimates.

Tips for Best Results

• Verify your source unit carefully — Selecting the wrong source unit (e.g., millilux instead of lux) will produce results off by a factor of 1,000. Double-check your meter's display unit before entering the value.
• Lux and lumen/m² are identical — If you see a specification in lm/m², it is numerically the same as lux. No conversion is needed between these two — they are just different notations for the same measurement.
• Nox equals millilux — The nox is simply another name for millilux (0.001 lx). Both units are used in low-light research, but "nox" is more common in European dark-sky studies.
• Use decimals for precision — The converter accepts decimal inputs. For low-light measurements (moonlight, starlight), you may need values like 0.25 or 0.0001. Use as many decimal places as your measurement warrants.
• Remember the lux-to-foot-candle shortcut — Divide lux by approximately 10 for a quick foot-candle estimate. Multiply foot-candles by approximately 10 for a quick lux estimate.
• Use the Sample button first — Click "Sample" to see a demonstration conversion before entering your own measurements.

Why Choose Amaze SEO Tools for Illuminance Conversion?

• 100% Free — No registration, no fees, and no limits on conversions.
• 9 Units Supported — Covers SI, CGS, imperial, and specialized units including microlux, nox, and phot.
• All-at-Once Results — Enter one value and see conversions to every other unit simultaneously.
• Accurate Calculations — Conversion factors are based on internationally recognized photometric standards.
• Clean, Organized Interface — Clearly labeled input field and dropdown make unit selection fast and intuitive.
• No Software Required — Runs entirely in your browser with no downloads, apps, or plugins needed.

Frequently Asked Questions (FAQ)

Q: Is the Illuminance Converter free?

A: Yes. The tool by Amaze SEO Tools is completely free — no account needed and no usage restrictions.

Q: What is the SI unit of illuminance?

A: The SI unit of illuminance is the lux (lx), defined as one lumen per square meter. It is the globally recognized standard used in building codes, lighting design standards, and scientific publications.

Q: What is the difference between lux and foot-candle?

A: Both measure illuminance but use different area bases. Lux is one lumen per square meter; a foot-candle is one lumen per square foot. Since a square meter is approximately 10.764 times larger than a square foot, 1 foot-candle equals approximately 10.764 lux.

Q: What is a phot?

A: The phot is a CGS (centimetre-gram-second) unit of illuminance equal to one lumen per square centimeter, which is 10,000 lux. It appears in older scientific literature and some specialized optical engineering applications but has been largely replaced by lux in modern usage.

Q: What is a nox?

A: A nox is a unit of illuminance equal to one millilux (0.001 lux). It was introduced specifically for measuring very low nighttime illuminance levels and is used in nocturnal ecology, dark-sky research, and light pollution studies.

Q: How much lux is needed for an office?

A: International standards typically recommend 300–500 lux (approximately 28–46 foot-candles) for general office work. Tasks requiring fine detail (drafting, electronics assembly) may require 500–1,000 lux. The European standard EN 12464-1 and the IESNA Lighting Handbook provide detailed recommendations by task type.

Q: Is lumen per square meter the same as lux?

A: Yes. They are numerically identical — 1 lux is defined as 1 lumen per square meter. The converter includes both as separate entries for convenience, since some specifications may list values in lm/m² notation rather than lux.

Q: Can I measure illuminance with my phone?

A: Many smartphones have ambient light sensors that can provide approximate lux readings using free light meter apps. However, phone sensors are not calibrated to laboratory standards and their accuracy varies significantly by device. For professional applications, use a dedicated lux meter (also called an illuminance meter or light meter).

Q: What is the illuminance of direct sunlight?

A: Direct sunlight at noon on a clear day produces approximately 100,000–120,000 lux (about 9,300–11,100 foot-candles or 10–12 kilolux). This value varies with latitude, altitude, atmospheric conditions, and time of year.

Q: Is my data stored or shared?

A: No. All calculations are performed within the tool in your browser. Your input values and conversion results are not stored, logged, or transmitted to any server.

Convert any illuminance measurement between 9 units instantly — use the free Illuminance Converter by Amaze SEO Tools to switch between lux, foot-candles, phots, nox, kilolux, and more for lighting design, photography, workplace compliance, and scientific applications!