PPFD Meter & DLI - Verdlux

Verdlux is a PPFD meter and plant light meter for your phone. Measure the light at your windowsill or under your grow light, see PPFD, lux and the daily light integral (DLI), and find out right away if it is enough for your plant.

EVERY LIGHT SOURCE IS FREE
Sunlight, overcast sky, warm and cool white LED, full-spectrum grow light, red/blue grow light, fluorescent, HPS, metal halide and incandescent. No light source sits behind a paywall, and none ever will.

WHAT YOU GET FOR FREE
• Live PPFD in µmol/m²/s, lux and an estimated DLI in mol/m²/day
• The light arc: your reading on a scale from shade to full sun, next to the range your plant needs
• Plant check for 73 houseplants, succulents, herbs, vegetables and seedlings: too dark, enough, ideal or too bright
• DLI calculator: PPFD and hours in, daily light out, with the plants that fit
• Stability indicator, so you know when a reading has settled
• Calibration for your phone, against a lux meter or against the PPFD chart of your lamp
• 3 saved spots with their latest readings
• Camera mode for phones without a light sensor
• Area map 3 × 3 for a grow tent or shelf, with average and evenness
• Try the lamp planner once with an optional video
Free with ads: a banner on the Spots and Tools tabs and now and then a full-screen ad at a natural pause, such as after saving or when you return after a break. Never during a measurement.

PRO: THE TOOLS FOR EVERY DAY
• Day measurement: leave the phone at the spot and Verdlux adds up the real light over hours, with the exact daily total and the plant check
• No ads: no banner, no full-screen ads, no videos
• Lamp planner: how high to hang your grow light and how long to run it for the plant you chose
• Unlimited spots and the full history with a season chart
• Light source detection with the camera
• Your light map without the Verdlux line, area map up to 5 × 5 and CSV export
Pro is available monthly, yearly or as a one-time purchase.

HONEST NUMBERS
Phones measure lux, weighted for the human eye. Verdlux converts lux into plant light with a published factor for each light source and shows you the formula. Phone sensors differ: without calibration a reading can be off by up to about 60 percent, after calibration typically 20 to 30 percent.

HOW TO MEASURE
Lay the phone flat at leaf height, screen up. Choose the light source and your plant, then save the reading at a spot such as "South window".

SHARE YOUR LIGHT MAP
One image with every spot in your home, its daily light and whether it suits the plant.

YOUR DATA
No account. Readings stay on your phone. The camera is only used live; no picture is stored or sent. Verdlux sends anonymous usage counts without a device ID. Ads come from our partner Unity (LevelPlay); you choose personalised ads in the consent dialog or later under Settings, Ad settings.

SOURCES
Conversion factors, light levels and plant needs come from published research and extension services:
Apogee Instruments: https://www.apogeeinstruments.com/conversion-ppfd-to-lux/
AGi32: https://docs.agi32.com/AGi32/Content/adding_calculation_points/PPFD_Concepts.htm
CIE: https://cie.co.at/datatable/cie-spectral-luminous-efficiency-photopic-vision
Purdue Extension: https://www.extension.purdue.edu/extmedia/ho/ho-238-w.pdf
HortScience 53(4): https://journals.ashs.org/view/journals/hortsci/53/4/article-p496.xml
HortScience 53(10): https://journals.ashs.org/view/journals/hortsci/53/10/article-p1407.xml
PubMed Central: https://pmc.ncbi.nlm.nih.gov/articles/PMC10322904/
University of Maryland Extension: https://extension.umd.edu/resource/lighting-indoor-plants
Cornell Cooperative Extension: https://s3.amazonaws.com/assets.cce.cornell.edu/attachments/75539/Growing_Conditions_for_Indoor_Plants.pdf
All sources are also linked inside the app.

Verdlux gives guide values for plant care. It is not a certified measuring instrument.

Questions or ideas: [email protected]