Understand the physical quantity
What is Candela, Lumens and Beam Angle?
Photometry describes light as weighted for human vision, while radiometry describes physical radiant power. Flux, intensity, illuminance, luminance, irradiance, wavelength, frequency, and photon energy are related but distinct quantities.
Remove the manual solid-angle step while keeping the uniform-intensity cone assumption visible.
The relationship
Keep quantity and basis explicit
For an ideal circular cone with uniform luminous intensity, solid angle Ω = 2π[1 − cos(θ/2)] steradians and luminous flux Φ = IΩ. Reverse modes solve I or θ.
See the workflow
What the calculator is doing
1Source or measured light2Apply geometry or spectrum3Photometric or radiant result
Worked context
Read the output in context
A uniform 1,000 cd source over a 60° full cone has solid angle about 0.841787 sr and luminous flux about 841.787 lm.
Interpret with care
Important boundary
Real beam intensity normally varies by direction, and a published beam angle may use a half-maximum convention rather than a hard uniform edge. Use photometric distribution data for design or compliance work.
The result does not select a lighting standard, certify compliance, predict perception, or replace calibrated photometry and optical design.
Browse Light & radiation for related physical quantities.
Quick guide
How to use this calculator
- Choose the photometric, radiometric, or photon relationship first, then enter measurements using the stated geometry and unit basis.
- Keep luminous and radiant quantities separate. The calculator performs only the declared conversion, reverse solve, geometry, or measurement summary and exposes useful intermediate values.
- Use companion outputs to reconcile the scenario, then retain the stated instrument, distribution, spectrum, geometry, and environmental boundaries before applying the result.
Calculation method
How the candela, lumens and beam angle calculator works
Remove the manual solid-angle step while keeping the uniform-intensity cone assumption visible.
For an ideal circular cone with uniform luminous intensity, solid angle Ω = 2π[1 − cos(θ/2)] steradians and luminous flux Φ = IΩ. Reverse modes solve I or θ.
Worked example
Candela, Lumens and Beam Angle example
A uniform 1,000 cd source over a 60° full cone has solid angle about 0.841787 sr and luminous flux about 841.787 lm.
For an ideal circular cone with uniform luminous intensity, solid angle Ω = 2π[1 − cos(θ/2)] steradians and luminous flux Φ = IΩ. Reverse modes solve I or θ.
Supported inputs
Precision and limits
Light and optics boundary
Real beam intensity normally varies by direction, and a published beam angle may use a half-maximum convention rather than a hard uniform edge. Use photometric distribution data for design or compliance work.
Units and precision
Calculations normalize compatible units once, retain working precision, and round only for display. Very small and large nonzero values use scientific notation; displayed precision cannot exceed the entered measurements or source data.
Decision boundary
This calculator does not select a lighting standard, certify compliance, predict perception, or replace calibrated measurement, photometric distribution data, optical design, or safety assessment.
Privacy
Entered values and results stay in this browser and are not sent to analytics or third parties.
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