Footcandles and Lux – How Much Lighting Do I Really Need?

Too dim and you’re squinting. Too bright and you’re wasting energy. Bad lighting hurts productivity, visibility, and safety. But the right level? That’s the game-changer.

Footcandles and lux are two units used to measure the amount of light hitting a surface. One footcandle equals one lumen per square foot, while one lux equals one lumen per square meter. Knowing the right light level for your space—measured in footcandles or lux—is critical to choosing the correct LED fixtures and ensuring proper visibility, efficiency, and comfort.

Let’s clear the confusion and figure out exactly how bright your space needs to be.

What Is the Difference Between Footcandles and Lux?

Footcandles and lux are both units of measurement used to describe illuminance—how much light falls on a surface. The difference lies in the unit system each one belongs to and how the measurement is calculated.

What Is a Footcandle?

A footcandle (fc) is mainly used in the United States and other countries following the imperial system.
– 1 footcandle = 1 lumen per square foot
If you’re working on a lighting plan in a U.S. warehouse, office, or shop, specs are likely listed in footcandles. It gives a practical way to understand how much light is hitting work areas, shelves, or floors.

What Is Lux?

Lux is the metric system’s equivalent to footcandles.
– 1 lux = 1 lumen per square meter
Lux is the standard unit of illuminance used across Europe, Asia, and most international lighting guidelines. It’s widely used in DIALux and lighting simulation tools.

How Do You Convert Between Them?

• 1 footcandle = 10.764 lux
• 1 lux = 0.0929 footcandles

This conversion helps you read or translate photometric data depending on your region’s standards.

What Is a Lumen?

A lumen measures the total light output from a source—regardless of how that light is directed or used.
– Think of lumens as the total power of the light.
– Footcandles or lux tell you how much of that light is actually useful on a surface.

Summary

Understanding these differences is key when designing lighting plans or comparing product specs—especially if you’re dealing with international standards.

How Do You Calculate Foot-Candle Lighting?

Calculating footcandles helps you understand how much light is reaching a surface—like a floor, workbench, or parking lot. It’s a key step in lighting design, especially for commercial or industrial spaces.

The Basic Formula

Footcandles = Lumens ÷ Area (in square feet)

This gives you the average illuminance across a surface.

Example:

Let’s say you have an LED fixture that outputs 10,000 lumens, and you’re using it to light an area that’s 500 square feet.

10,000 ÷ 500 = 20 footcandles

That means, on average, your surface will receive 20 footcandles of light.

What This Number Tells You:

• Low-use areas (like storage rooms): 10–20 footcandles is usually enough
• Office or retail spaces: 30–50 footcandles
• Workshops or task areas: 50–100+ footcandles

Things That Also Affect Lighting:

Even if the math checks out, footcandle levels can still vary depending on:
– Fixture layout (how evenly lights are spaced)
– Mounting height (higher lights spread light wider but dimmer)
– Beam angle (narrow beams concentrate light; wide beams spread it out)
– Reflective surfaces (light-colored walls or floors can bounce light back and increase brightness)

If you’re planning a large space or want precision, it’s worth using a lighting simulation tool like DIALux or consulting a supplier who can provide a photometric plan. That way, you’re not just calculating—you’re optimizing.

What Is the Formula for Calculating Lighting?

If you want to figure out how many LED fixtures you need to light a space properly, there’s a simple two-step formula. It helps ensure you get enough brightness without over-lighting or wasting energy.

Step 1: Calculate Required Lumens

Use this formula:

Required Lumens = Area (sq ft) × Recommended Footcandles

Different areas require different footcandle levels.
– Warehouses: 20–30 footcandles
– Offices or classrooms: 30–50 footcandles
– Workshops or precision areas: 50–100 footcandles

Step 2: Calculate Number of Fixtures

Now divide the total lumens by the output of each fixture:

Number of Fixtures = Required Lumens ÷ Lumens per Fixture

Example:

Let’s say you’re lighting a 1,000 sq ft workspace that needs 30 footcandles:

• Required Lumens = 1,000 × 30 = 30,000 lumens
• If each LED fixture produces 5,000 lumens:
• Number of Fixtures = 30,000 ÷ 5,000 = 6 fixtures

Tips for Better Accuracy:

• Consider fixture placement and mounting height
• Factor in beam angle and room reflectivity
• Add extra buffer if shelves or machinery may block light

This formula is a solid starting point, especially for general lighting plans. For more complex layouts, photometric simulations provide a deeper, room-by-room analysis.

How Much Lighting Do I Need?

Lighting needs vary depending on what you’re doing in the space. A storage room doesn’t need the same brightness as a workshop or retail floor. The key unit to watch is footcandles (fc), which measure how much light actually reaches a surface.

Here’s a quick guide based on typical lighting tasks:

Storage Room: 5–10 fc

This is soft lighting—enough to navigate shelves or find boxes, similar to hallway light levels.

Warehouse: 20–30 fc

Bright enough to safely move around, read labels, and load or unload pallets.

Assembly Line: 50–75 fc

Clear, task-specific lighting to spot fine details, align parts, or check quality control. You need consistent, shadow-free coverage.

Retail Store: 30–50 fc

Good lighting makes products look better and helps customers see clearly. Higher brightness can also affect shopper mood and behavior.

Office: 30–50 fc

Comfortable brightness for reading, typing, and screen work without eye strain. Lighting should be even and glare-free.

Workshops: 70–100 fc

High-brightness lighting is crucial for tool use, detail work, or precision measurement. You want clean, shadow-free illumination.

Rule of Thumb:

• The more detailed the task, the more footcandles you need.
• Start low for ambient spaces. Go higher for safety and productivity zones.

Need help calculating your exact lighting levels? Use this guide with a lighting formula or contact someone who can run a photometric layout for your space.

IES Recommended Lighting Levels

The Illuminating Engineering Society (IES) provides industry-standard lighting level recommendations to ensure safe, efficient, and comfortable environments. These guidelines help lighting designers, engineers, and facility managers choose the right brightness for each type of space.

Here’s a quick breakdown of IES recommendations based on footcandles:

Corridors and Stairwells: 5–10 footcandles

This level gives safe navigation lighting without being overly bright.

Lobbies and Reception Areas: 10–20 footcandles

Enough for a welcoming atmosphere and easy recognition of faces and signage.

Classrooms: 30–50 footcandles

Provides good visibility for reading, writing, and teaching without causing glare.

Laboratories: 75–100 footcandles

High-intensity lighting is essential for precision tasks and clear visibility of instruments and samples.

Mechanical Rooms: 20–30 footcandles

Bright enough for equipment inspection and routine maintenance.

Parking Garages: 10–15 footcandles

Ensures safety and visibility for both drivers and pedestrians in low-ceiling spaces.

What Does 30 Footcandles Look Like?

Picture a well-lit office or clean industrial warehouse—uniform, shadow-free lighting that’s easy on the eyes and perfect for general tasks.

Here’s a simple table to guide your planning:

Tip:
30 footcandles is similar to a bright, evenly lit office or warehouse—clear and comfortable for visual tasks without glare.

IES standards help balance light performance with energy use. Using the right footcandle levels prevents both under-lighting (which affects safety and productivity) and over-lighting (which wastes energy and creates glare).

If you’re working on a project and want to meet IES levels without overdoing the wattage, just use these guidelines as your baseline.

Summary

Understanding footcandles and lux helps you dial in the exact lighting you need. It’s not about brighter—it’s about better. With the right lighting levels, you boost safety, improve comfort, and cut waste.

Still unsure how many footcandles your space needs? Contact us directly—we’ll help you calculate, design, and deliver the perfect LED lighting plan.