Lumen Depreciation Calculator

Measurements and entries

Keep lumens, candela, lux, and foot-candles on the correct geometric basis. If operating conditions changed between readings, calculate separate cases.

Convert units once, retain the original reading, and verify the converted magnitude. If you also need remaining capacity, continue with Battery Capacity Fade Calculator.

Initial lumens

Default example: 10000 lm. Enter initial lumens in lm.

Lumen maintenance

Default example: 80%. Enter lumen maintenance in %.

From inputs to result

The displayed result follows maintained lumens = initial × maintenance fraction. Its variables correspond to Initial lumens and Lumen maintenance.

The initial scenario returns 8,000.00 lm. Re-enter field data before using the answer in a design or comparison.

Calculate maintained lumens from initial lumens and lumen maintenance. When that related quantity matters, continue with Candela Lumens Calculator.

Using the answer downstream

Record initial lumens and lumen maintenance with maintained lumens. Include the operating state and data source.

Pass maintained lumens with all available digits during downstream arithmetic. Round at the final reporting step.

How to use the result

Use Maintained lumens as one quantified check within the larger decision. Compare it with illuminance, uniformity, driver loading, voltage loss, energy use, and maintained output.

Label alternate cases rather than overwriting the baseline. Continue to Lumens Watts Calculator if lamp power is also needed.

Before accepting the number

A plausible-looking output does not prove that the entries are compatible.

Recheck decimal placement and unit conversion when the answer looks unusual.

Checks before using the answer

Dirt and room-surface depreciation may require additional factors.

Outside the entered variables, consider fixture distribution, reflections, mounting, maintenance, and meter position. Test an additional scenario when an omitted effect has a plausible range.

Record reflectance, maintenance condition, beam definition, and measurement location. The next worksheet may be Lux Lumens Calculator if average illuminance is needed.

Before carrying the answer forward

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

After calculating maintained lumens, compare its magnitude with initial, maintained, and worst-case lighting conditions. An independent order-of-magnitude check can reveal a misplaced decimal or unit prefix.

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 Lumen Depreciation