Luminous Intensity & Beam Candela Calculator

Photometry, SI Base Units & Luminous Intensity Metrology

Luminous Intensity is the luminous flux emitted per unit solid angle in a specific direction:

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• Universal Luminous Intensity Conversion Formulas (BIPM & CIE Standards)**:

1 Candela (cd) = 1 lm/sr = 1.019368 Candlepower (cp) = 1.10742 Hefnerkerze (HK)

I_cp = I_cd0.981 = I_cd × 1.019368

1 Carcel unit = 9.74 cd | 1 Millicandela (mcd) = 0.001 cd

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• Solid Angle, Beam Lumens & Inverse Square Law**:

Ω = 2π ( 1 - (θ) / (2) ) (Solid Angle in Steradians, sr)

Φ = I_cd × Ω (Total Luminous Flux in Lumens, lm)

E = I_cdd^2 (Incident Illuminance in Lux at Distance d)

d_ANSI Throw = √(I_cd)0.25 Lux = 2 × √(I_cd) (Meters)

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• Standard Lighting & Optoelectronic Benchmarks**:

• PCB Indicator LED: 20.0 mcd = 0.020 cd Φ = 0.0169 lm (60^ cone)

• Standard Paraffin Candle: 1.0 cd 1.019 cp Φ = 12.57 lm (isotropic 4π sr)

• Tactical LED Flashlight: 25,000.0 cd 25,484 cp d_throw = 316 m

• Automotive High Beam: 50,000.0 cd 50,968 cp E = 500 Lux @ 10m

• Lighthouse Beacon: 1,000,000.0 cd 1,019,368 cp d_throw = 2,000 m

How to Use This Calculator

Enter your Luminous Intensity (I_v / Candela) (e.g. 50000 in intensity), From Luminous Intensity Unit — choose from Candelas (cd = lm/sr - SI Base Unit), Candlepower (cp - Legacy British Standard), Hefnerkerze (HK - German Amyl Acetate Standard), To Luminous Intensity Unit — choose from Candlepower (cp), Candelas (cd), Hefnerkerze (HK), Beam Spread Angle (2θ in degrees) (e.g. 20 in °), Target Distance (d in meters) (e.g. 10.0 in m), and Lighting & Optoelectronic Benchmark — choose from Custom Luminous Source, Automotive LED High Beam (50,000 cd @ 20° cone) → 50,968 cp | 55,371 HK | E = 500 Lux @ 10m | 4,773 lm in beam, Standard Wax Candle (1.0 cd, isotropic 4π) → 1.019 cp | 1.107 HK | 12.57 Lumens total. Results update instantly as you type — adjust any value to compare scenarios.

The Formula

Multipliers to SI Base Unit Candela (cd = lm/sr) (BIPM & CIE Standards)

ANSI FL1 Beam Distance to 0.25 Lux (Moonlight threshold): d_throw = sqrt(I / 0.25) = 2 * sqrt(I)

Worked Example

An automotive lighting engineer specifying a 50,000 cd LED headlight calculates that at a distance of 10 meters, the beam delivers exactly 500.0 Lux on the road, with an ANSI FL1 reach of 447 meters.

Understanding Your Result

Unit conversions are exact by definition within a given measurement system (e.g., 1 km = exactly 1,000 m). Cross-system conversions (metric to imperial) use defined exchange factors: 1 inch = exactly 2.54 cm; 1 pound = 0.45359237 kg. Round your converted result to match the precision of your original measurement — expressing more decimal places than your input justifies implies false accuracy. For regulatory, legal, or safety-critical applications, verify which measurement system is required by the applicable standard.