Lighting
Dimmer Load Calculator
Use Dimmer Load when dimmer loading is the quantity you need. Enter connected lamp power and dimmer rating, then compare the answer with the equipment or operating limits that apply to your case.
Calculate Dimmer loading
Keep every entry on the units shown below.
Values this page needs
Use photometric data for the actual fixture, optic, mounting height, and task plane. Nameplate and meter values are not interchangeable unless they describe the same condition.
Values used below a division bar must stay positive. Use the displayed unit for every field and document conversions separately. Pair this page with Generator Load Percentage Calculator when reviewing generator loading.
- Connected lamp power
- Default example: 420 W. Enter connected lamp power in W.
- Dimmer rating
- Default example: 600 W. Enter dimmer rating in W.
Understanding the equation
The displayed result follows loading = load ÷ rating × 100. The participating entries are Connected lamp power and Dimmer rating.
For the example shown, dimmer loading equals 70.00%. Treat that value as a demonstration, not a recommendation.
Calculate dimmer loading from connected lamp power and dimmer rating. If you also need daylight factor, continue with Daylight Factor Calculator.
What the number means
The primary answer, Dimmer loading, describes only the entered scenario. Compare it with initial, maintained, and worst-case lighting conditions.
Save the raw entries before testing another scenario.
Transferring the result
Archive connected lamp power and dimmer rating with dimmer loading. Identify the instrument, rating, or assumption behind each entry.
Transfer dimmer loading with all available digits during downstream arithmetic. Keep a separate displayed value if reporting precision differs.
Where this estimate can fail
LED compatibility cannot be inferred from watts alone.
The arithmetic intentionally leaves out daylight variation, control behavior, depreciation, and spatial uniformity. Do not hide omitted behavior inside an unexplained correction factor.
Use photometric data for the actual fixture, optic, mounting height, and task plane.
Before carrying the answer forward
Review dimmer rating and the remaining entries as one case. If one value belongs to another temperature, load, or time period, separate the scenarios.
After calculating dimmer loading, compare its magnitude with illuminance, uniformity, driver loading, voltage loss, energy use, and maintained output. 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 fixture distribution, reflections, mounting, maintenance, and meter position.
Questions about inputs and assumptions
How do I run a useful sensitivity check?
Use separate labeled cases when more than one condition changes. Record reflectance, maintenance condition, beam definition, and measurement location.
Does the answer include a design margin?
No. Compare the value with the fixture photometric file and the measured task plane and apply relevant equipment and installation requirements.