Candela Lumens Calculator

Changing Lumens in beam

Change Lumens in beam from 1000 lm to 1200 lm without altering the remaining fields. The calculated value shifts from 833.33 cd to 1,000.00 cd.

Do not average the two cases if either could define an operating limit.

Formula used on this page

Here, Luminous intensity is obtained from candela = lumens ÷ steradians. Only Lumens in beam and Beam solid angle enter the numerical result.

For the example shown, luminous intensity equals 833.33 cd. Treat that value as a demonstration, not a recommendation.

Calculate luminous intensity from lumens in beam and beam solid angle. For the companion illuminance calculation, open Inverse Square Lighting Calculator.

Input notes

Use photometric data for the actual fixture, optic, mounting height, and task plane. If operating conditions changed between readings, calculate separate cases.

A denominator entry cannot be zero. Convert units once, retain the original reading, and verify the converted magnitude. Another relevant worksheet is Phase Shift Time Calculator.

Lumens in beam

Default example: 1000 lm. Enter lumens in beam in lm.

Beam solid angle

Default example: 1.2 sr. Enter beam solid angle in sr.

How to use the result

Read Luminous intensity as the outcome of this equation, not as automatic equipment approval. Compare it with illuminance, uniformity, driver loading, voltage loss, energy use, and maintained output.

Store the measurement state and conversion notes with the answer.

Transferring the result

Archive lumens in beam and beam solid angle with luminous intensity. Identify the instrument, rating, or assumption behind each entry.

Carry luminous intensity at its stored precision for dependent calculations. Keep a separate displayed value if reporting precision differs.

Assumptions and limitations

Real beams are not perfectly uniform.

The arithmetic intentionally leaves out fixture distribution, reflections, mounting, maintenance, and meter position. Test an additional scenario when an omitted effect has a plausible range.

Keep lumens, candela, lux, and foot-candles on the correct geometric basis.

Before carrying the answer forward

Check the source of beam solid angle before calculating. A credible result requires every field to describe the same physical condition and unit basis.

The displayed luminous intensity should be checked against initial, maintained, and worst-case lighting conditions. Investigate an unexpected magnitude before changing the model or adding margin.

Keep a baseline and vary the least certain measurement first. A separate analysis may be needed for driver efficiency, optical loss, surface reflectance, and beam-edge definition.

Questions about Candela Lumens