Measure lux, PPFD and DLI with your iPhone

Lux-525 Pro turns the sensors already in your phone into a light meter that reads illuminance, photosynthetic photon flux, daily light integral, color temperature and luminous flux — no external hardware, no dongles.

Download on the App Store

Free · iOS 15.5 or later · 16MB · English

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What it does

Five readings at once

Illuminance in lux or foot-candles, PPFD/PAR, daily light integral, luminous flux in lumens and color temperature in kelvin — all live, all on one screen.

Built for growing, not just for rooms

PPFD and DLI are the numbers that matter when you are placing plants under a grow light. Set the photoperiod and the app works out the daily total for you.

Pick your light source

Converting lux to PPFD depends entirely on the spectrum. Choose from full-spectrum LED, red+blue, red+blue+white, 2700K white, incandescent, halogen, CFL 6500K or natural daylight, and the maths follows.

Calibrated against a real meter

The readings were tuned against a professional light meter rather than left to the raw sensor value, which is where most phone light meters fall down.

Unit converter included

Lux to PPFD, PPFD to lux, lux to DLI, PPFD to DLI, lux to lumens, lumens to lux, lux to foot-candles and back — without leaving the app for a web calculator.

Keep or send your readings

Save a measurement to the phone or send it out by message or email when you need a record of what a spot actually receives.

How it works

1

Tell it what the light is

Select the source from the list — LED, halogen, CFL, daylight and so on. This is what makes the PPFD and DLI numbers trustworthy.
2

Hold the phone where the plant is

Or where the desk, the canvas or the work surface is. Readings update in real time as you move.
3

Read, convert, save

Take the number you need, convert it into another unit if you want, and save or share the measurement.

Questions

Do I need any extra hardware? +

No. Lux-525 Pro uses sensors that are already in the iPhone, so there is no dongle, diffuser cap or Bluetooth accessory to buy.

Can I use it to check grow lights for plants? +

That is what the PPFD, PAR and DLI readings are for. Select the type of light you are using, hold the phone at canopy height, and you get the photon flux at that spot and the daily total for your photoperiod.

Why do I have to choose a light source first? +

Because converting a lux reading into PPFD depends on the spectrum of the light. A 2700K white LED, a red+blue grow light and midday sun all deliver very different photon counts at the same lux value, so the app needs to know which one it is looking at.

What is the difference between lux, PPFD and DLI? +

Lux describes brightness as a human eye perceives it. PPFD counts the photons plants can actually use, per square metre per second. DLI is the total those photons add up to over a whole day, which is PPFD combined with how many hours the light is on.

How accurate is it compared with a dedicated meter? +

The app is calibrated against a professional light meter and is intended for personal use. It will not fully replace an industrial-grade instrument, but it is considerably closer than an uncalibrated sensor reading.

Which units does it support? +

Lux and foot-candles for illuminance, micromoles per square metre per second for PPFD, micromoles per square metre per day for DLI, lumens for luminous flux and kelvin for color temperature.

Is Light Meter free? +

The app is free to download from the App Store. Some capabilities are unlocked through an in-app purchase; the current terms are always shown inside the app before you buy.