How To Calculate Lux

How do I calculate lux - the formula?

Lux level = total light output (lumens) / area (square meters)
total light output = lumens per fixture * number of fixtures

Therefore

number of fixtures = (Lux level * area) / lumens per fixture

You need to look up the manufacturer data for your light fitting to get the lumens per fixture. For example a standard 100W incandescent bulb is around 1400 lumens.

Example:

Desired lux level = 175, Room size = 16 m2

Fixtures = 175 * 16 / 1400 = 2

So you'd need 2 100W incandescent light fittings.