Lux Meter: PPFD Light Meter

Lux Meter is a practical light meter, PPFD meter, grow light meter, and DLI calculator for indoor plants, grow lights, seedlings, herbs, vegetables, houseplants, orchids, and more.
Measure ambient light in Lux, estimate PPFD, calculate DLI, and quickly understand whether your plants are receiving too little, enough, or too much light.
Designed to be fast and easy to use, Lux Meter helps you optimize grow light intensity, daily light duration, and light distribution using your phone’s built-in light sensor.
REAL-TIME LUX METER
Use your phone’s light sensor to measure ambient light instantly.
View live readings for:
• Lux
• PPFD
• DLI
Measurements update in real time as you move your phone closer to or farther from the light source.
PPFD METER FOR GROW LIGHTS
Convert Lux readings into estimated PPFD (Photosynthetic Photon Flux Density) based on the selected light source.
Supported light types include:
• Full Spectrum LED
• White LED
• Sunlight
• Fluorescent
• HPS
• Red / Blue Grow Lights
A modern PPFD gauge shows whether the current light level is Very Low, Low, Good, High, or Very High for the selected plant target.
DLI CALCULATOR
Calculate Daily Light Integral (DLI) using PPFD and daily light duration.
Lux Meter can also calculate:
• Required PPFD for a target DLI
• Required daily light hours
• Expected DLI from current PPFD
PLANT LIGHT TARGETS
Choose a plant category and compare current PPFD and DLI with a recommended range.
Presets include:
• Seedlings
• Herbs
• Leafy Greens
• Houseplants
• Orchids
• Succulents
• Tomatoes
• Peppers
• Flowering Plants
SMART LIGHT GUIDANCE
Based on current PPFD, DLI, plant target, and light duration, Lux Meter provides practical suggestions such as:
• Move the light closer
• Increase light intensity
• Increase daily light duration
• Reduce light intensity
• Increase the distance from the light
If DLI is too low, the app can estimate how many hours of light are needed to reach the target.
All recommendations are calculated locally using built-in rules. No AI is required.
PPFD LIGHT MAP
Check how evenly your grow light covers a growing area.
Create 3×3, 4×4, or 5×5 Light Maps and measure multiple points across a grow tent, shelf, seed tray, plant rack, or indoor garden.
View:
• Average PPFD
• Minimum PPFD
• Maximum PPFD
• Light Uniformity
The heat map makes it easy to identify dark spots and uneven grow light coverage.
HOLD MEASUREMENT
Wait for the reading to stabilize, then tap Hold. Lux, PPFD, DLI, gauge, and light status remain frozen so you can move the phone and read the result comfortably.
SAVE MEASUREMENTS
Save measurements and keep a local history for different grow tents, plant shelves, windows, seed trays, indoor gardens, or light setups.
SENSOR CALIBRATION & SMOOTHING
Choose Fast, Balanced, or Stable smoothing.
You can also apply manual sensor calibration when comparing readings with another trusted light meter.
MANUAL MODE
If your device does not provide a usable light sensor, you can still enter Lux or PPFD manually and use the DLI calculator, plant targets, and light recommendations.
WORKS OFFLINE
Core measurement features work offline.
• No account required
• No cloud sync
• No AI
• Local measurement history
• Measurements stay on your device
IMPORTANT NOTE
PPFD values calculated from a smartphone light sensor are estimates. Accuracy may vary depending on the phone’s sensor, light spectrum, device design, sensor range, and calibration.
For professional or scientific measurements, use a dedicated PAR meter or quantum light meter.