Lux to Lumen Calculator
Convert lux (lx) to lumens (lm): lm = lx × A. Use area in m² or ft², or isotropic sphere radius. Reverse lumens to lux. Runs locally in your browser.
Trust summary Engine tested · Specification checked · v1.1.0
- Input interpretation
- Enter values to calculate.
- Result
- —
- Model
- Luminous flux from illuminance and area (or sphere radius), or illuminance from flux and area.
- Scope
- Uniform illuminance over the stated area or sphere
- Verification
- Engine tested · Specification checked · v1.1.0
- Named expert review
- Optional · Not performed
- Specification basis
- 1 lx = 1 lm/m²; 1 m² = 10.76391 ft²; sphere A = 4πr²
Formulas
Core equations used by this calculator.
How to use
Choose mode
lx → lm with m², ft², or sphere; or the reverse lm → lx paths.
Enter lux (or lumens) and area / radius
Use the work-surface size, or sphere radius for an isotropic model.
Read lumens or lux
Higher lux or larger area → more lumens required.
Example calculations
Common configurations with formula and result.
500 lx · 10 m²
Default (area)
500 lx · 100 ft²
Feet area
80 lx · r = 1 m
Full sphere
Office desk target
500 lx · 2 m²
lm → lx
1000 lm · 10 m²
Typical illuminance targets (guide)
Common values at a glance.
| Activity | Approx. lux | Notes |
|---|---|---|
| Public / dark outdoor | 20–50 | Orientation |
| Corridors / storage | ~100 | Circulation |
| Classroom | ~300 | EN workplace guide |
| Office / PC work | ~500 | Common desk target |
| Detailed / drawing work | 1000–2000 | Higher visual demand |
| Outdoor construction (varies) | 20–200 | Task-dependent |
Lux to Lumen calculator specification
Version 1.1.0 · Engine tested
- Engine tested 4 published cases
- Named expert review Not performed
- Calculation version 1.1.0
- Definition
- Lux (lx) is illuminance — lumens per square meter. Lumens (lm) are total luminous flux. With uniform coverage over area A: lm = lx × A(m²). With A in ft²: lm = 0.09290304 × lx × A(ft²). For uniform lux on a sphere of radius r: lm = lx × 4πr².
- What it calculates
- Luminous flux from illuminance and area (or sphere radius), or illuminance from flux and area.
- Inputs
- Lux (lx) or lumens (lm)
- Area (m² or ft²) or sphere radius (m)
- Outputs
- Lumens (lx → lm) or lux (lm → lx)
- Formula
Φ=E·A; Φ=E·4πr²- Assumptions
- Uniform illuminance over the stated area or sphere
- All flux reaches that surface
- Units
- lx, m² → lm
- lx, ft² → lm
- lx, r(m) → lm
- Boundary conditions
- A = 0 or r = 0 → lux path undefined (UI returns 0)
- Example
- 500 lx, 10 m² → 5000 lm
- Validation cases
4 published on this page
- 500 lx, 10 m² → 5000 lm
- 500 lx, 100 ft² → ≈ 4645.15 lm
- 80 lx, r = 1 m → ≈ 1005.31 lm
- 1000 lm, 10 m² → lx → 100 lx
- Specification basis
- 1 lx = 1 lm/m²; 1 m² = 10.76391 ft²; sphere A = 4πr²
- Calculation version
- 1.1.0
Background
Interpretation and common distinctions.
Convert lux (lx) to lumens (lm) by multiplying by the illuminated area.
Phi((lm)) = E((lx)) × A((m^(2))) Phi((lm)) = 0.09290304 × E((lx)) × A((ft^(2)))
Default: 500 lx · 10 m² → 5000 lm.
Lux vs lumens
| Unit | Measures |
|---|---|
| Lux (lx) | Light received per m² on a surface |
| Lumen (lm) | Total light emitted by the source |
Use lux for task/room targets; convert to lumens to size lamps for a known area.
Sphere (isotropic) model
When lux is uniform on a sphere of radius r:
Phi = E × 4π r²
Use the sphere tabs for this path (radius in meters).
Related tools
Other calculators in this family: Lumen to Lux, Lux to Candela, Lumen to Watt, Foot-Candles to Lux .
Frequently asked questions
Key distinctions behind the calculation.
How do I convert lux to lumens?
Multiply by area in square meters: lm = lx × A. With area in ft²: lm = 0.09290304 × lx × A(ft²).
What is the difference between lux and lumens?
Lux is light on a surface (per m²). Lumens are total light output. Same lamp can give different lux depending on distance and beam spread.
How many lumens do I need for 500 lux?
It depends on area: for 10 m², lm = 500 × 10 = 5000 lm (ideal uniform coverage). Real layouts need more because of losses and uniformity.
When do I use the sphere mode?
When modeling uniform illuminance on a sphere of radius r: lm = lx × 4πr². For flat desks and floors, enter the actual area.
Does distance matter?
Indirectly — farther away usually means a larger lit footprint for the same beam, so you need more lumens (or a tighter beam) to hold the same lux.
Does this include optical losses?
No. The calculator assumes all flux reaches the area uniformly. Use utilization and light-loss factors for fixture layouts.
Can I convert lumens back to lux?
Yes — use lm → lx: lx = lm ÷ A for the same area.
Is 1 lux equal to 1 lumen?
Only over exactly 1 m². Over 10 m², 1 lx requires 10 lm.