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PAR meter APPs tested & compared for accuracy

Can PAR meter apps measure PAR accurately?

An accurate quantum sensor for measuring PAR cost over $350, way out of reach of most home growers. However, there are a number of smartphone apps which allow you measure PAR (Photosynthetically Active Radiation, the wavelengths of light that grow plants), turning your phone into a Par Meter.

I have tested the PPFD App and the Photone App and compared them to an industry standard Quantum PAR meter.

PPFD App for Android and IOS 

The PPFD App has been around for a few years on Android and is now also available on IOS. I tested the PPFD App on a Samsung S22 and iPhone 12.

There is an option to use the phone front camera on its own but it is much more accurate to use a paper diffuser over the camera lens. This is very easy to do, just tape a small piece of white printer paper over the front camera when taking the readings.


PPFD App with diffuser


The PPFD app is free and allows selection of a range of spectrum sources such as various LED spectrum and HPS.

It also provides an excellent PAR map feature where you can create your own PAR map and get a visual image of the PAR spread as well as system efficiency and average PAR readings.

Learn how to make a PAR map here


PPFD App screen shots


I also tested an android phone with the PPFD app paired by bluetooth to the Uni-T lux meter. In theory this should provide a more accurate readings as android front camera sensors vary in sensitivity and the Lux meter sensor should be consistent.


PPFD App paired with the UNI-T Lux meter by bluetooth

Photone App for IOS

I also tested the Photone App for IOS which is on the market for a number of years. It has less functionality than the PPFD app and only 1 spectrum source is available for free. 


Photone App screen shots


Par meter Apps tested against a Quantum PAR sensor

I took measurements for the two most common grow light spectrum on the market today. The LED spectrum is a mid temperature white light at 3500K CT and 660nm red diodes. I also tested with a 600W HPS bulb (all HPS bulbs emit a very similar spectrum). 

I measured with the different App configurations and compared to the readings from an Apogee SQ500 quantum sensor.

I hung the light source over a 3ft x 3ft or 90cm x 90cm test area with reflective walls and took 36 PAR measurements across the test area with each device.

The distance between the light source and the sensor was the same in each test.

I selected the LED light source of '3500K + 10% 660nm red' for the PPFD app.

I selected the 'LED full spectrum' source for the Photone app.

I did not calibrate the sensor for either app. There instructions how to do so on each app.

LED light source (3500K +10% 660nm red)
PPFD App Photone App
PAR meter SQ500 iPhone + diff Android + diff Android + Uni-T iPhone + Uni-T iPhone +diff
Average PAR (µmols/m²/sec)
669 715 410 764 761 709
Variance Reference +7% -39% +14% +14% +6%



HPS grow light source
PPFD App Photone App
PAR meter SQ500 iPhone + diff Android + diff Android + Uni-T  iPhone + Uni-T  iPhone +diff
Average PAR (µmols/m²/sec) 670 548 382 612 608 737
Variance Reference -18% -43% -9% -9% +10%


Conclusion of PAR meter apps test

The Photone App and PPFD App are fairly accurate when used with an iPhone. This is mainly due to the consistent sensitivity of the iPhone front camera across all iPhone models.

The PPFD App is quite accurate when paired with the UNI-T lux meter for both the iPhone and Android phones. This setup does not rely on front camera sensitivity so should be reliable and repeatable across all android phone brands and models.

The PPFD app was not accurate when used with an android phone and no calibration. To calibrate you need a known source and repeatable reading. This is not easy to do and likely to result in inaccuracies.

The features of the PPFD app are far superior and much more functionality on the free version. If you have an iPhone or you can pair it with the UNI-T lux meter I would recommend it over the Photone App. Otherwise the Photone App on iPhone is the most accurate setup.




4 thoughts on “PAR meter APPs tested & compared for accuracy


Using the Uni-T with a conversion factor which you evaluated in one of your videos is still the way to go. Very linear behaviour and still beating any of the offsets in this test of PAR apps.

June 19, 2024 at 15:21pm
Robert Miller

I got one of the uni ts Bluetooth models off ebay I find the reading to be pretty close to the par maps from factory but it’s good to know their is a variance. Cheers

June 19, 2024 at 15:21pm

Have you tested the Photone Android app? After reading this i dont know what to trust. Im using a Android phone and it would be nice to know if it showing the right reading.

April 12, 2022 at 14:23pm

how to interpret the data. I have no clue on how to use the data i have on quantum light meter. i have 3 data taken at 5 days interval

April 12, 2022 at 14:24pm

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