PAR and PPFD Meter Apps for iOS: 2022 Edition

Light is such an important factor for plant growth and wondering about your plants’ lighting can certainly keep you up at night. Luckily enough there is a simple solution that does not cost an arm and a leg: A light meter app.

I tested all relevant plant light meter apps on the App Store so you don’t have to. This article provides an overview and recommendations about them. So read along to find the iOS plant light meter app that is right for you!

Are You an Android User?

If you’re looking for an Android app, check out my other article entirely focused on Android.

What Makes a Good Plant Light Meter

As a baseline for our test, we first need to identify what makes a good plant light meter — or in this case specifically: A good plant light meter app. For amateurs and professional growers alike, I identified the following criteria:

1. The plant light meter shall be easy-to-use
2. The plant light meter shall measure PAR as PPFD
3. The plant light meter shall be accurate and precise
4. The plant light meter shall be cost-efficient
5. The plant light meter shall be well maintained (supporting the latest devices, offering support, etc.)

I’ll cover each of these criteria in my subsequent test and recommendation to gain you the peace of mind needed when it comes to choosing your light meter app.

iOS Plant Light Meter Apps

A quick search on the App Store reveals many light meter apps. Most of them are targeted to be used in photography while some of them act as a simple illuminance meter. We want to measure PAR / PPFD for our plants (and not illuminance in lux or fc as this is for humans) and there is only one app able to measure PAR / PPFD, so I’ve included other illuminance-based plant light meter apps from the App Store into the comparison as well.

Accuracy Comparison

As we are first and foremost comparing light meters, they need to measure accurately. My tests revealed that only two apps do so and that’s why they’re at the top of my recommendations.

A small error is to be expected as no light meter exactly measures the same, but any error exceeding 10% becomes noteworthy whereas errors upwards of 30% even become dangerously critical in some scenarios.

Illuminance (Light for Humans)

I measured various light intensity levels using all light meters as described. The results are very interesting with large deviations between the different light meter apps as can be seen in the charts below:

PAR / PPFD (Light for Plants)

As for the PAR / PPFD measurements, I again measured different light intensity levels using the Apogee quantum PAR sensor as the reference and Photone in its PAR meter configuration. The results can be seen in the charts below:

You can find how I took those measurements towards the end of this article.

My Recommendations

Recommended for Everyone: Photone — Grow Light Meter

The Photone — Grow Light Meter is the only plant light meter app on the App Store that is measuring even close to accurate and provides everything that is needed: PAR measurements, real-time DLI calculations, illuminance measurements and even the color temperature (CCT) in kelvin. Photone also includes helpful guides and a calculator for cannabis, houseplants, and fruits and vegetables to assist our grow lighting decisions. The app can be used for free and also includes additional features, content, and fast 24 hour support with the optional Pro subscription.

Tolerable for Beginners: Plant Light Meter

The Plant Light Meter app is well-made and backed by a professional and active developer. It also includes a database of common houseplants and their lighting requirements that may be especially useful for beginners. I want to recommend this app but use it for grow lighting decisions with extreme caution as it really lacks the accuracy to do so.

As a side note on measuring, it is the only app that measures reflected light instead of incident light and outputs the result as a range. I therefore took the average of the displayed value as the measurement for the comparison.

Recommended, but not for Plants: Light Meter LM-3000

The Light Meter LM-3000 is made by the same developer as Photone — no surprise that it is just as accurate. However, it serves as a general-purpose lux meter and is not made specifically for plants. If you only need a reliable and trustworthy lux and foot-candle measurement, the LM-3000 is the way to go.

Not Recommended: Lux Light Meter Pro

The Lux Light Meter Pro app developed by Marina Polyanskaya seems to be widely used and ranks first in the App Store search. Using it has a learning curve attached, but once you get the hang of it, you can operate the app somewhat reliably. However, the app is infrequently maintained, pretty pricey (unless you like ads), and most importantly: Very inaccurate.

Not Recommended: Plant Light Meter LUX & Care

Plant Light Meter LUX & Care is a new app that wasn’t available when I took this test in 2021. The user interface looks appealing and the app is very easy to use. It offers you a free trial (whilst also showing ads) to take three measurements. After that, you need to pay a hefty fee of $3 as a weekly subscription. As with the others, the Plant Light Meter LUX & Care isn’t accurate enought to serve as a plant light meter.

Not Recommended: The Helios

The Helios is another new app just released in 2022. The app looks promosing and well-made with a simple and intuitive user interface and an active developer that is frequently publishing new releases. Still, it isn’t accurate and also pretty expensive if you opt for the weekly subscription.

Not Recommended: Flora — Houseplant Care

The Flora — Houseplant Care app feels different (and not in a good way) as it is just loading a website that comes with many quirks and issues. The UI is very basic but also pretty nested. Even though the app is free, following its lighting advice can cost you your plants and I don’t recommend doing so.

Other Light Meter Apps

There are other light meter apps that claim to measure illuminance (lux / fc) available in the App Store. I took a look at “Luminous Meter”, “Lux Meter — light measurement tool”, “Light Meter — measure luminosity”, “Galactica Luxmeter”, “Light Lux Meter”, “Whitegoods Lightmeter”, “Nurus Light Wellness”, and “Light Meter +”. However, none of these were even remotely usable as a light meter and I therefore didn’t include them in this test. I don’t recommend using any of the aforementioned apps.

Test Methodology

Lighting

I wanted to perform a test that is both accurate and representative for the usage in growing plants. I therefore used two of the most common grow lights: A full spectrum LED Quantum Board, that is used by many home- and professional growers alike, and a “blurple” Phlizon Red / Blue LED. I put each lamp fixture into a light proof grow box and varied the height to achieve different light intensity levels.

Reference Meter

To provide the PAR reference measurements, a NIST traceable Apogee SQ-520 Full-Spectrum Smart Quantum Sensor (costing around $500) was used.

Phone

All iOS apps were tested on an iPhone 11 Pro running iOS 15 and also with the most recent app version available from the App Store as of April 2022.

Closing Thought

For me, this 2022 update has been an interesting test: Many apps claiming to do the same, yet they are completely different. I hope that this article is comprehensible and makes sense. If you have any inputs, please let me know! If you think that my measurements are flawed: Please challenge me! Recreate a stable test setup and measure those apps against an accurate and reliable reference. I’m very curious and would be pleased to see your results as well.

The measurements above provide me with absolute confidence that the Photone Grow Light Meter is an excellent alternative to any hardware PAR meter — especially at a $500 price difference!