Lighting level

Recommended Light Levels (Illuminance) for Outdoor and Indoor Venues 

This is an instructor resource with information to be provided to students as the instructor sees fit.Light Level or Illuminance, is the amount of light measured in a plane surface (or the total luminous flux incident on a surface, per unit area).

The work plane is where the most important tasks in the room or space are performed.

lighting level calculator

Measuring Units of Light Level - Illuminance

Illuminance is measured in foot candles (ftcd, fc, fcd) or lux (in the metric SI system). A foot candle is actually one lumen of light density per square foot; one lux is one lumen per square meter.

• 1 lux = 1 lumen / sq meter = 0.0001 phot = 0.0929 foot candle (ftcd, fcd)

• 1 phot = 1 lumen / sq centimeter = 10000 lumens / sq meter = 10000 lux

• 1 foot candle (ftcd, fcd) = 1 lumen / sq ft = 10.752 lux

Common and Recommended Light Levels Indoors 

The outdoor light level is approximately 10,000 lux on a clear day. In the building, in the area closest to windows, the light level may be reduced to approximately 1,000 lux. In the middle area its may be as low as 25 - 50 lux. Additional lighting equipment is often necessary to compensate the low levels.

Earlier it was common with light levels in the range 100 - 300 lux for normal activities. Today the light level is more common in the range 500 - 1000 lux - depending on activity. For precision and detailed works, the light level may even approach 1500 - 2000 lux.

The table below provides recommended light levels from the IESNA Lighting Handbook and LPD levels from the IECC 2015. Check your local jurisdiction for other or more stringent requirements. The US General Services Administration provides lighting levels and LPDs for US Government buildings, which can be used as a guide for other types of buildings.

The required light levels are indicated in a range because different tasks, even in the same space, require different amounts of light. In general, low contrast and detailed tasks require more light while high contrast and less detailed tasks require less light.


Room TypeLight Level (Foot Candles)Light Level (Lux)IECC 2015 Lighting Power Density (Watts per SF)
Bedroom - Dormitory20-30 FC200-300 lux0.38
Cafeteria - Eating20-30 FC200-300 lux0.65
Classroom - General30-50 FC300-500 lux1.24
Conference Room30-50 FC300-500 lux1.23
Corridor5-10 FC50-100 lux0.66
Exhibit Space30-50 FC300-500 lux1.45
Gymnasium - Exercise / Workout20-30 FC200-300 lux0.72
Gymnasium - Sports / Games30-50 FC300-500 lux1.20
Kitchen / Food Prep30-75 FC300-750 lux1.21
Laboratory (Classroom)50-75 FC500-750 lux1.43
Laboratory (Professional)75-120 FC750-1200 lux1.81
Library - Stacks20-50 FC200-500 lux1.71
Library - Reading / Studying30-50 FC300-500 lux1.06
Loading Dock10-30 FC100-300 lux0.47
Lobby - Office/General20-30 FC200-300 lux0.90
Locker Room10-30 FC100-300 lux0.75
Lounge / Breakroom10-30 FC100-300 lux0.73
Mechanical / Electrical Room20-50 FC200-500 lux0.95
Office - Open30-50 FC300-500 lux0.98
Office - Private / Closed30-50 FC300-500 lux1.11
Parking - Interior5-10 FC50-100 lux0.19
Restroom / Toilet10-30 FC100-300 lux0.98
Retail Sales20-50 FC200-500 lux1.59
Stairway5-10 FC50-100 lux0.69
Storage Room - General5-20 FC50-200 lux0.63
Workshop30-75 FC300-750 lux1.59
lighting level calculation

Lighting Calculation Formula

Lighting Level Calculator is a tool to calculate the level of lighting in a room. The Lumens of different popular lamps  are provided in this calculator, so that entry of this data is made easy and you do not have to look up this information every time. The calculations are based on the room cavity ratio.

You have to input the length, width and height of the room and the software automatically calculates the area and the corresponding lighting  level. These parameters can be stored by this calculator for later use in other calculations.

The values can be entered by the keyboard or by the use of the mouse. There are input boxes with up and down arrows on the sides, for increasing or decreasing the value in the box. You can calculate the lighting level of a room, for a given amount of lamps and their lumens. You can alternatively find out how many lamps, with how much of lumens, will be required to give a specified level of lighting.

If you change any of the variables, there is a corresponding dynamic change in the values.

Once you know how many lumens you need, you can start figuring out how many light bulbs will suffice to illuminate your surface. To do it, use the formula below:

bulbs = lumens / BL

BL stands for the number of lumens that a light bulb emits. You can usually find this number on the bulb packaging. It's a much better indicator of the bulb's luminosity than the wattage, as LED lights often need less power than regular light bulbs.

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