Lumen to Millicandela Converter & LED Intensity Calculator

Lumens, Millicandela (mcd), LED Viewing Angles & Optoelectronic Metrology

Light-emitting diodes (LEDs) emit light over a specific directional cone shaped by their epoxy lens or primary silicon dome optics:

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• Lumen to Millicandela Conversion Formula**:

I_v (mcd) = Φ_v (lm)Ω × 1,000

Ω = 2π (1 - ((θ) / (2)))

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• Viewing Angle Impact on Perceived Brightness**:

• For the exact same 1.0 Lumen optical power:

• At 15^ Narrow Spot Lens: Ω = 0.0537 sr I_v = 18,620 mcd

• At 30^ Standard 5mm LED: Ω = 0.2142 sr I_v = 4,669 mcd

• At 60^ Flood Optic: Ω = 0.8418 sr I_v = 1,188 mcd

• At 120^ Bare SMD Chip: Ω = 3.1416 sr I_v = 318 mcd

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• Standard LED Component Benchmarks**:

• SMD 0805 Status Indicator: 0.20 lm @ 120^ 63.7 mcd PCB power indicator

• Diffused 5mm Green LED: 2.0 lm @ 160^ 375.4 mcd Wide-angle indoor indicator

• High-Brightness 5mm Clear LED: 5.0 lm @ 30^ 23,346 mcd = 23.35 cd

• Automotive DRL LED: 50.0 lm @ 45^ 330,400 mcd = 330.4 cd

• Cree XP-G3 Power LED: 300.0 lm @ 125^ 90,300 mcd = 90.3 cd

How to Use This Calculator

Enter your Luminous Flux (Lumens / lm) (e.g. 5.0 in lm), From Luminous Flux Unit — choose from Lumens (lm - Total Optical Power), Millilumens (mlm = 10⁻³ lm), LED Viewing Angle / Beam Apex (2θ in degrees) (e.g. 30 for narrow LED, 120 for SMD in deg (°)), To Intensity Unit — choose from Millicandela (mcd = 10⁻³ cd - Standard LED Spec), Candela (cd = lm/sr - SI Standard), Kilocandela (kcd = 1,000 cd), Number of LED Emitters in Array (e.g. 1 in LEDs), and Optoelectronic & LED Package Benchmark — choose from Custom LED Flux & Viewing Angle, 5mm T-1 3/4 Water-Clear LED (5.0 lm @ 30° Narrow) → 23,346.0 mcd (23.35 cd), SMD 0805 Micro Indicator (0.20 lm @ 120° Wide Angle) → 63.66 mcd. Results update instantly as you type — adjust any value to compare scenarios.

The Formula

On-axis Lux at 1 meter: E(1m) = I_v (in cd)

Worked Example

An electronic circuit designer selects a 5mm indicator LED rated at 5.0 Lumens with a narrow 30° lens and calculates it produces 23,346 mcd of luminous intensity, ensuring sharp daylight visibility on an outdoor industrial control panel.

Understanding Your Result

Unit conversion precision: round to the same number of significant figures as your original measurement. Converting 6 feet to meters gives 1.8288 m — but if your measurement was approximate (±1 inch), expressing more than 2 decimal places is false precision. For international trade and technical specifications, SI units (meters, kilograms, liters) are the standard. US customary units (feet, pounds, gallons) differ from Imperial UK units: 1 US gallon = 3.785 L vs. 1 UK gallon = 4.546 L.