Foot Candle Calculator — Convert FC to Lux and Find Your Target
Convert foot-candles to lux instantly and calculate the total lumens you need for any room.
FC ↔ Lux Converter
Lux
538 lx
Formula
fc × 10.764
Lumens Required
Total Lumens Needed
5250 lm
This foot candle calculator sits next to the main recessed light calculator, and the two work together: convert your target foot-candle level here, then plug the lumen total into the main tool to get an exact fixture count. A foot-candle is the imperial illuminance unit that U.S. electricians, code officials, and lighting designers use to describe how bright a space actually is at the surface where people work, read, or walk.
What a Foot-Candle Actually Measures
One foot-candle equals one lumen of light spread evenly over one square foot of surface. Picture a single candle held one foot from a wall. The light landing on a one-square-foot patch of that wall is close to one foot-candle, which is where the name comes from. The unit goes back to nineteenth-century photometry, when a standard candle was the reference light source labs used to calibrate meters. Modern LEDs don't burn like candles, but the math still works the same way. Take the total lumens a fixture puts out, divide by the area it lights, and you get the foot-candle level at that surface.
Foot-candles measure illuminance, meaning light landing on a surface. That's different from lumens, which measure total light output, and different from CRI, which measures how accurate colors look under that light. A 1,000-lumen downlight can deliver 40 fc (430 lx) over a small desk or spread the same output across a whole bedroom and land at 10 fc (108 lx). The fixture doesn't change. Only the area it covers changes the foot-candle result.
Foot-Candles vs Lux: Converting Between the Two
Foot-candles and lux measure exactly the same thing: illuminance. The difference is the unit system. The U.S. uses imperial foot-candles; most of the rest of the world uses metric lux. The conversion factor is fixed: 1 fc = 10.764 lx. That number comes from area math. One square meter equals 10.764 square feet, so the same lumen output spread over a square meter reads as 1 lux, but the same lumen spread over the smaller square foot reads as 10.764 times more concentrated, or 1 foot-candle.
Lux = Foot-Candles × 10.764
Foot-Candles = Lux ÷ 10.764
If a spec sheet from a European fixture manufacturer lists 300 lx, divide by 10.764 to get roughly 28 fc, which is the number you'd compare against a U.S. code minimum written in foot-candles. Our lux converter runs the same math starting from a lux number if that's what you have on hand.
IES Foot-Candle Targets by Space Type
The Illuminating Engineering Society, usually shortened to IES, publishes recommended illuminance ranges for dozens of space types in its Lighting Handbook. The table below lists the ranges most homeowners and contractors need for residential and light-commercial recessed lighting jobs, given in both foot-candles and lux so you can check a spec sheet written in either unit.
| Space | Target fc | Lux |
|---|---|---|
| Parking / Storage | 5–10 fc | 54–108 lx |
| Corridor | 10 fc | 108 lx |
| Bedroom | 15 fc | 161 lx |
| Living Room | 15–20 fc | 161–215 lx |
| Dining Room | 15–20 fc | 161–215 lx |
| Office | 40–50 fc | 430–538 lx |
| Kitchen Ambient | 35–40 fc | 377–430 lx |
| Kitchen Task | 75–100 fc | 807–1,076 lx |
| Bathroom Vanity | 70 fc | 753 lx |
| Garage | 20–30 fc | 215–323 lx |
| Laundry / Utility Room | 30–40 fc | 323–430 lx |
| Workshop | 50–100 fc | 538–1,076 lx |
Treat these as targets, not hard rules. A reading chair or a vanity mirror needs the higher end of its range. A room used mostly for casual evening lounging can sit at the lower end, especially once the fixtures are on a dimmer.
How to Measure Foot-Candles in a Room
A calibrated digital light meter gives the most accurate reading. Hold it flat, sensor facing up, at the height where the activity happens: desk height in an office, counter height in a kitchen, the floor in a hallway. Take three readings per zone. Read directly under a fixture, read again in the gap between two fixtures, and read once more at the darkest corner of the room. Average the three numbers instead of relying on the brightest spot you happened to measure.
Phone Apps as a Quick Check
A smartphone lux app works fine for a rough check but not for a code inspection. Point the phone's light sensor at the work surface, note the lux reading, and divide by 10.764 to get foot-candles. Build in some margin for error. Phone sensors typically read 10 to 20 percent low compared with a calibrated meter, and cheap apps can be off by more. Treat the app number as a floor, not a precise measurement.
When to Hire a Lighting Professional
Call a lighting designer or electrician when the numbers matter for code compliance, such as a commercial tenant improvement, an egress stairwell, or a parking structure, or when a large open-plan space needs several brightness zones reconciled at once. A professional brings a calibrated meter, knows the exact code section an inspector will cite, and can run a full point-by-point lighting calculation instead of the simplified average-lumen method this page uses.
Worked Example: Sizing a Home Office by Foot-Candles
Say you're lighting a 12×10 ft home office, 120 sq ft total, and want the IES office target of 40 fc (430 lx) at desk height.
Step 1 — Convert the target to lux. Useful for cross-checking any European fixture specs: 40 fc × 10.764 = 430 lx, rounded.
Step 2 — Total lumens needed = 120 sq ft × 40 fc = 4,800 lm
Step 3 — Fixture count = 4,800 lm ÷ 900 lm per fixture = 5.3 → round up to 6 fixtures
Step 4 — Check the real-world result. Six 900-lumen fixtures deliver 5,400 lumens across 120 sq ft, which works out to 45 fc (484 lx), a bit over target. That's normal, because light loss factors such as dust, fixture age, and wall color usually pull the delivered level down 10 to 20 percent from the calculated number.
Step 5 — Verify with a meter after installation. Set the meter on the desk, take three readings, and average them. If the average lands between 35 and 45 fc (377 and 484 lx), the layout is doing its job. If it reads well under 35 fc (377 lx), add a fixture or switch to a higher-lumen bulb.
Why Foot-Candles Matter for Recessed Lighting Layouts
Every recessed lighting plan starts with a foot-candle target, not a fixture count. Pick the number first, such as 15 fc (161 lx) for a bedroom or 40 fc (430 lx) for a kitchen, and the rest of the layout follows from it: total lumens needed, then fixture count, then spacing. Skip that first step and you're guessing. Guessing usually means buying six downlights because that's what the last room used, then finding out the new room is twice the size and lands at half the intended brightness.
The foot-candle number also drives spacing once you move to a full grid layout. A high-fc task room like a kitchen needs fixtures closer together and more of them per square foot than a low-fc room like a hallway, even when both rooms use identical downlights. Get the foot-candle target right first, and the fixture count and spacing calculations that follow will deliver the light level the room actually needs, not just a grid that looks even on paper.
Frequently Asked Questions
What is a foot-candle?
A foot-candle (fc) is one lumen of light spread over one square foot of surface, equal to about 10.764 lux. It's the imperial illuminance unit used by U.S. building codes and the IES Lighting Handbook to describe how bright a surface actually is.
How do I convert foot-candles to lux?
Multiply foot-candles by 10.764 to get lux. For example, 50 fc × 10.764 = 538 lux. To go the other way, from lux to foot-candles, divide the lux number by 10.764.
How many foot-candles does a kitchen need?
Plan on 35–40 fc (377–430 lx) for ambient kitchen lighting and 70–100 fc (753–1,076 lx) over islands and prep counters. The gap between ambient and task levels is normal; task zones always run brighter than the rest of the room.
How do I measure foot-candles at home?
Use a digital light meter, or a smartphone lux app with the reading divided by 10.764. Take the reading at the height where the work happens, such as desk or counter height, not at the floor, and average a few spots rather than trusting one reading.
What's the minimum foot-candle level for safe walking?
Hallways and stairs need at least 5 fc (54 lx) at the walking surface for safe navigation. Bump that to 10 fc (108 lx) for households with older occupants or anyone with reduced night vision.
Why are foot-candles still used in the U.S.?
Because U.S. building codes, energy codes such as Title 24 and the IECC, and IES standards are all written in foot-candles. Most American product spec sheets and lighting designs quote fc first and lux second, if at all.