Lux Level Calculator

Measure light for seedlings, herbs, and houseplants quickly. Choose a method, enter values, and get conversions. Make smarter lighting decisions for healthier plants every day.

Calculator

White theme • Responsive inputs

Choose a method and enter your measurements. The calculator supports lux, lumens, area, foot-candles, and an optional PPFD estimate.

Pick what you want to solve for.
Use manufacturer lumen rating for a fixture.
Use the area receiving most of the light.
Conversions are handled automatically.
Use a phone meter or handheld light meter.
Helpful when reading older horticulture charts.
PPFD is an estimate, not a lab measurement.
Use a factor from your fixture’s datasheet.

Saved calculations (last 15)

Time Mode Lux Lumens Area fc PPFD
No history yet. Run a calculation to save it here.
Exports use the most recent saved result.

Example data table

Scenario Inputs Outputs Use case
LED over herbs 5,000 lm, 2.0 m² 2,500 lx, 232.3 fc Check if basil and mint are in medium light.
Target greens 8,000 lx, 1.2 m² 9,600 lm required Size fixtures for lettuce and spinach indoors.
Convert chart 300 fc 3,229 lx Use foot-candle recommendations from a guide.
PPFD estimate 10,000 lx, white LED ≈135 µmol/m²/s Quick check for seedling trays and cuttings.
Numbers are illustrative; measure at plant height for best results.

Formula used

  • Lux (lx) = Lumens (lm) ÷ Area (m²) — assumes reasonably even distribution.
  • Lumens (lm) = Lux (lx) × Area (m²) — useful for fixture sizing.
  • Foot-candles (fc) = Lux (lx) ÷ 10.76391 and Lux = fc × 10.76391.
  • PPFD ≈ Lux × k — where k depends on spectrum; use a datasheet factor when available.
  • Area conversion: m² = ft² × 0.09290304.

How to use this calculator

  1. Select a calculation method based on what you know.
  2. Enter lumens, area, lux, or foot-candles as required.
  3. Use the same measuring point: plant canopy height.
  4. Submit to see results above the form under the header.
  5. Download CSV or PDF for record keeping and comparisons.
Practical tip: Average readings from 4–9 spots to reduce hotspots.

Related Calculators

energy use calculatorwire ampacity calculatorsolar battery size calculatorjunction box size calculatorsunrise time calculatorsunset time calculatordmx universe calculatorsolar tilt angle calculatorled retrofit savings calculatorlumens per square meter calculator

Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.