Illuminance Converter

This page converts an illuminance from one unit into another. Every value passes through the lux, the SI unit illuminance is held in, and illuminance stays illuminance: a unit only converts inside its own dimension.

How do you convert illuminance between lux and foot-candles?

Pick the unit you have, pick the unit you want, and type the value. The page multiplies by the factor between the two and prints the arithmetic under the result, so the answer and the working are the same object.

1. Choose the unit your value is in. This page opens on the lux.
2. Choose the unit you want it in. This page opens on the foot-candle.
3. Type the value. The result and the factor behind it appear together.
4. Read the working. It converts into the lux first and out again, which is the same two lines you would write by hand.

Illuminance Conversion Table

One row per unit this page offers, each measured against the lux. The last column says whether the factor is a definition or a reading of one.

Worked Examples

The question the bank ranked highest for this page, answered with the working.

Where These Factors Come From

Every number above is read from the knowledge base rather than computed for the page. These are the statements it holds for illuminance.

• One lux is one lumen per square metre. One foot-candle is one lumen per square foot, which is 10.763910416709722 lx, and one phot is exactly 10 000 lx.
• An SI prefix multiplies a unit by a power of ten: k is 10^3, M is 10^6, G is 10^9, m is 10^-3, micro is 10^-6 and n is 10^-9. The prefix belongs to the unit, so 1 kV is 1000 V.
• An exact factor is a definition rather than a measurement. 1 in = 25.4 mm and 1 lb = 0.45359237 kg were fixed by the 1959 international yard and pound agreement, so they never gain another digit.
• How this page reports a result result in the target illuminance unit

SI prefixes on this page

Lux, Lumens or Candelas?

A candela measures how bright a source is, a lumen measures the light it sends out, and a lux measures how much of that light lands on a surface. This page converts illuminance, so it works in lux and foot-candles and turns none of the three into another.

The rule behind this factor is the same for every unit - the SI base units.

Frequently Asked Questions

Related Conversions

• Temperature sits in the same measurement group as illuminance - convert a temperature between Celsius and Fahrenheit.
• If you are measuring volumetric flow rate rather than illuminance, scale a flow rate up or down instead.
• If you are measuring power rather than illuminance, the watt-based factor table instead.
• If you are measuring parts-per ratio rather than illuminance, parts per million, billion and trillion instead.
• If you are measuring energy rather than illuminance, convert energy between joules and kilowatt-hours instead.
• If you are measuring digital storage rather than illuminance, convert digital storage between bytes and gigabytes instead.

The rest of the family sits on back to the unit converters.