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Keep The Guesswork Out of Grow Lighting

Measure PAR / PPFD, Lux, Kelvin:
All with an app

Grow Light Meter App

The revolutionary
Light Meter App
you can trust


Go Pro:

Set up your plants’ lighting with a proper PAR light meter.

Korona is the light meter app that allows you to take all the light measurements relevant for your plants and for all widely used grow light technologies.


  • PAR / PPFD in µmol/m²s

  • Illuminance in Lux and foot-candle

  • Light temperature in Kelvin

Your Benefits

Built for Grow Lights

We actively develop, test, and optimize for the widely used grow lights in the market.

No Costly Equipment

Korona only requires your smartphone’s camera — nothing else.

Tailored to Plants

Measure PAR in µmol/m²s and even calculate your plant’s DLI at the palm of your hand.

Proven Accuracy

Compared to various common hardware light meters, Korona is repeatedly achieving the lowest average error rates in measuring grow light illuminance.

Average Error

31.7 %
Light Meters
5.1 %
iPhone X


4.7 %
iPhone 7
4.2 %
iPad Pro

More information regarding measurement and evaluation details on the above error rates can be found in our white paper.

White Paper

What Our Users Think

out of 5
vitvorg, 01/21/2020
Useful and user friendly with a very involved attentive developer!
Best app on the AppStore to estimate PPFD for growing plants. I’m a botanist, and so I know this app won’t replace a $400 par meter, but for quick estimations with your phone? This app is more than worth it. The hold feature is super useful. The background shows a grainy picture that gives you instant feedback that you are aiming your phone correctly, which is a unique feature that even the expensive PAR meters do not have. A suggestion to the developer for a future update would be for the background preview picture to freeze when the hold option is used. The hold option right now freezes the reading which is useful for measuring at actual leaf locations and orientations, but the background picture does not freeze with the reading. It would be amazing for the background image to freeze with the hold measurement, so when you pull your phone back you could see that you were aiming the phone correctly and you could see what you were aiming at when the hold measurement was taken.
Funmcfunster, 07/26/2020
I put my foot in my mouth.
Originally, I had written a review stating how displeased I was for paying $5 for the Full-Spec LED addon. Then, I decided to see what others had said in their reviews of the app, and found an interesting bit of information that really helped me. I was getting inaccurate PPFD reading (300 directly next to a light source for plant cultivation), and was absolutely baffled by the number I got. However, I noticed multiple people, as well as the developer state that the use of a diffuser (like a tissue) is important in some instances. I just tried this and feel the PAR reading is incredibly more accurate than what I originally thought it to be. My apologies to the developer, and thank you to everyone for bringing useful information to the reviews. I would certainly now recommend this app knowing what I do.
Crankdoctor, 02/24/2020
Helped so much.
I tried a couple apps and nobody had one for different lighting so this was a great step above. I purchased a new grow light and had it to low and to high for a week. Almost toasted my plants. I could only find around about how high I needed it on web. I seen this app and it could read led white and red together so I was on it! Needles to say it put me in the sweet spot and plants are loving light now thanks to this app. It’s a game changer. I’m sold!

Reviews and Mentions

How to Use

Korona is used in many ways to optimize grow lighting. The following represents some examples to get you started.


Identify where and how high to hang your lamp

Learn More

Duration and Power

Regulate how long and how strong your lights are on

Learn More


Identify when a light bulb needs to get replaced or cleaned

Learn More


Korona is available for iPhone and iPad.
It's free.

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