Everything You Ever Wanted to Know About Foot Candles But Were Afraid to Ask
Let’s start with the definition...
What is a “foot candle”?
A foot-candle (or foot-candle, fc, lm/ft2, or ft-c) is a measurement of light intensity. One foot-candle is defined as enough light to saturate a one-foot square with one lumen of light.
Source: FSG
But what does that really mean? Rather than measuring the amount of light that leaves a light source (lumen output), foot-candle measurements focus on how much light actually reaches a surface area.
For example, a foot-candle describes the amount of light on the ground surface beneath a parking lot light, not the output of the parking lot light itself.
Here are some typical foot-candle measurements for given light conditions:
- Unobstructed sunlight: 10,000 fc
- Overcast sunlight: 100 fc
- Visually intensive workspace: 200 fc
- Store environment: 5 fc
- Residential space (living): 5-40 fc
- Residential space (working): 70-90 fc
It’s worth noting that “foot-candles” are the standard unit of light measurement in places that use United States customary units. In Europe and other parts of the world where metric units are used, “lux” is used instead. Lux is essentially the same measurement as foot-candles, but it defines the illuminated area as one square meter rather than one square foot.
What is the Purpose of a Foot-Candle?
So what’s the use of a measurement like foot-candles? Simply put, the idea is to ensure that spaces requiring specific light levels are actually receiving those levels. This is particularly important in electrical construction as well.
Offices, manufacturing facilities, warehouses, and workrooms require significantly higher foot-candle readings to make work easier and less stressful on the eyes. Experienced lighting contractors know the ins and outs of warehouse lighting standards, as well as the many types of facilities that require specialized lighting.
Source: FSG
Hallways and lobbies, on the other hand, need much lower foot-candle readings — the light doesn’t need to be bright enough for people working over reports and keyboards. Instead, it only needs to be bright enough to show off the decor and keep people from tripping, without being so bright that it feels harsh or sterile.
Source: FSG
Many organizations have special lighting requirements, and foot-candles are the best way to ensure the right amount of light is reaching the right surfaces.
Museums need precise light levels to create the appropriate ambiance and protect sensitive artifacts. Horticulture requires very accurate foot-candle readings to make sure plants receive the right amount and type of light. Movie and video producers carry foot-candle meters with them to verify the right light levels on their subjects.
Any business with physical security requirements also needs to be aware of foot-candle readings in sensitive areas and around cameras and entry points.
Without the right light, we simply can’t live and work the way we need to. If you have requirements for how much light needs to reach a specific space, you’ll want to know how many foot-candles are landing on that surface.
How to Measure Foot-Candle Readings
Measuring foot-candles falls under the broader scientific discipline of photometry. Photometry is the measurement of light as our eyes perceive it. This is distinct from radiometry, which is the measurement of all radiant energy, including light, in absolute terms.
Measuring light as our eyes interpret it matters to businesses and organizations of every kind, because you need to know what your customers and staff are actually experiencing every time they work or shop in one of your buildings.
Really, light is a tool for your business. Like any tool, it produces different effects in different settings. In public areas, lower and warmer light tends to work best; in work areas, bright light is typically needed. Foot-candle readings are how you confirm your lighting tool is doing its job properly.
The most reliable instrument for taking foot-candle readings is a quality light meter. Light meters are available from many manufacturers at a wide range of price points, some as affordable as $20, others at $200 or more. The right meter for your application is one that is both accurate and fast.
Source: iStock
Most light meters output readings in foot-candles or lux (the SI-derived equivalent that measures a one-meter square rather than a one-foot square).
If your meter reads in lux and you need foot-candles, just remember this number: 10.764. Divide your lux reading by 10.764 to get foot-candles. Quick math: 1 lux equals 0.092903 foot-candles.
How Many Lumens are in a Foot Candle?
A lumen measures the total amount of light produced by a source. A foot-candle measures how much of that light reaches a surface. One foot-candle equals 1 lumen per square foot.
Foot Candles vs Lux?
Foot-candles are the imperial unit and lux is the metric unit for the same measurement. Foot-candles measure lumens per square foot; lux measures lumens per square meter. 1 foot-candle equals 10.76 lux. If your light meter only reads in lux, divide by 10.76 to convert to foot-candles.
Use these resources to improve your commercial lighting.
What to do with Foot-Candle Readings?
If you want to get serious about making light levels work for your organization, understanding how foot-candles are measured is the right starting point.
If readings fall below IES recommended guidelines — or simply aren’t bright enough for the application — you need to either increase the lumens in your existing fixture or replace it with a fixture that offers more output or better efficiency.
For example, the IES (Illuminating Engineering Society) recommends 10 foot-candles for parking garage spaces. If you’re reading 7 foot-candles in a lighted area of your parking garage, you need more lumens. Depending on the replacement lamps available for your fixture type, you may be able to increase light levels with a straightforward 1-for-1 lamp swap.
If you’re dealing with shadows or dark areas, the fix often involves adding new LED fixtures or upgrading existing ones to better distribute light from each lamp. In sports lighting — like tennis court lighting — shadows or significant dips in foot-candle levels can create real problems for players during events.
Source: FSG
A light meter remains the most accurate way to evaluate brightness and light distribution in any space.
Foot Candles in Action: Lighting Strategies from Austin to Los Angeles
When planning a lighting upgrade, understanding foot candles is essential to getting the right brightness for your space. Businesses in Austin are using foot-candle standards to design energy-efficient lighting solutions that meet both code requirements and comfort goals.
In Dallas, our commercial lighting experts help facility managers determine the right foot-candle levels for offices, warehouses, and retail spaces. In Los Angeles, where sustainability and compliance go hand in hand, getting light levels right can also support local energy codes and LEED goals. Whatever city you’re in, understanding foot candles is the first step toward smarter, safer lighting.
Need Help with Foot-candle Readings?
Using light meters to test a given space, then adjusting the light appropriately, is the secret to reducing eye stress, fatigue, and headaches among your staff. It’s the secret to making your store floor look inviting and irresistible for customers. It’s the secret to using light to the best of your ability, and to your greatest advantage.
But do you want to do it yourself?
Using light meters to test a space — then adjusting accordingly — is the key to reducing eye strain, fatigue, and headaches among your staff. It’s the key to making your store floor look inviting to customers. It’s the key to using light to your greatest advantage.
But do you want to do it yourself?
Your job is to run your business as well as you can — and that job never ends. There are always higher-priority things you should be doing besides running photometric tests and adjusting light levels. That’s true for everyone on your team too: their job is to make things run better, more smoothly, and more efficiently.
To get the most out of your facilities, you need experts. If you don’t already have lighting specialists on your team, FSG is the answer. We know you and your team don’t have time to run your own tests and adjust your own settings — that’s exactly why FSG makes it easy.
Call us at (512) 886-1253 or contact us here and tell us about your lighting challenges. Need lights brighter or dimmer? Not sure what’s appropriate for a given environment? Let’s talk — we’re here to help your business do what it does, better. And if you just need supplies right now, visit FSG Storefront to shop online.
Frequently Asked Questions
What’s the difference between lumens and foot-candles?
Lumens measure how much light a source produces. Foot-candles measure how much of that light actually reaches a surface — expressed as lumens per square foot. It’s a more practical metric for evaluating how bright a space actually feels at working height.
How do I convert lux to foot-candles — and why does 10.764 matter?
Divide your lux reading by 10.764 (or 10.76) to convert to foot-candles. The number exists because lux measures lumens per square meter while foot-candles measure lumens per square foot — and there are 10.764 square feet in a square meter.
How do I measure foot-candles in a room correctly?
Use a light meter and take readings at the height where work actually happens — typically desk height, not the floor. Take multiple readings across the space to evaluate both overall brightness and distribution.
What’s a good foot-candle level for offices, warehouses, and retail spaces?
OSHA standards and IES guidelines define minimums — like ~5 fc in active work areas and ~10 fc in aisles for certain industrial lighting applications — but most facilities are designed to higher levels for productivity and quality.
- Warehouses: 10–20 fc for storage aisles; 20–50 fc for packing, inspection, and active tasks
- Offices: 30–50 fc at the desk/workplane
- Retail: 30–75 fc ambient; 50–200 fc on displays depending on brand and contrast goals
If my foot-candle readings are too low, do I need new fixtures — or are there other options?
Not always. Low readings can often be improved by increasing lumens (via lamp or fixture upgrade), switching to a more efficient fixture, or improving light distribution to reduce shadows and dark zones. In some systems, a straightforward 1-for-1 lamp replacement is enough to bring levels up to where they need to be.
