Take the guesswork out of grow lighting! Measure PAR / PPFD, Lux, fc, and Kelvin: All within the most accurate light meter app out there.

Setting up your plants' optimal lighting is not easy — if not impossible without a proper PAR / PPFD plant light meter. Calculating your indoor garden's daily light integral (DLI) to match your plants’ needs allows you to optimize your lighting for maximal yield at minimal electricity consumption.

Our Korona grow light meter app measures photosynthetically active radiation (PAR) as PPFD in µmol/m²s, calculates the daily light integral (DLI) in mol/m²d, and measures illuminance in foot candles or Lux. It also allows you to measure light temperature in Kelvin which can help you determine if a light is suitable for fruiting and flowering or for vegetative growth.

It is by far the most accurate light meter app for plants and achieves industrial grade accuracy that easily compares to dedicated and expensive quantum PAR meters for many hundreds of dollars. You can learn more on how we achieve over 95% of accuracy against research grade laboratory equipment and how to achieve maximum accuracy by yourself in our white paper:

The app also contains useful guiding articles to help you get the most out of your plant lighting. In addition, you can find more informative and educational content on our blog:

Wondering how much light your plants need? The plant lighting calculator on our website helps you to dial in your lighting to your specific plants' needs:

Our Korona Pro subscription enables to access all supported light sources, measure light temperature in Kelvin, and receive our premium support – and there’s even more to come in the future!

The subscription is auto-renewable and automatically renews unless auto-renew is turned off at least 24 hours before the end of the current period. Your account will be charged for renewal at the price listed within 24 hours prior to the end of the current period. Subscriptions made on iOS devices can be managed and auto-renewal turned off in Account Settings for your Apple ID after purchase. Once purchased, refunds will not be provided for any unused portion of the term.

You can find our terms of service on our website:

What’s New

Version 2.4.0

We added new guides to the info page. They will help you to better use our application and achieve even greater results with your grow lighting. We've also fixed some minor bugs along the way :)

Ratings and Reviews

4.5 out of 5
329 Ratings

329 Ratings

Dasistgass ,

Nice layout and concept inaccurate.

Thanks for developing this aesthetic piece of software.

Wish the faceid sensors could be used... it seems to use basic info from the camera sensor.

It's unfortunately less accurate than a free photography light meter app..

I dont doubt a diffuser would help a lot but idk..

I calibrated against a decently accurate lux meter .

I even gave the software the benefit of the doubt by using reflected light ( shouldnt need diffuser)

And it still was inaccurate.

It can still def be used to see the footprint of light for gardening applications . Even if the meter isnt accurate its better than no meter. I cant use it for film photography unfortunately...

It would be nice if they would throw in a photography light meter mode ( automatically telling you what settings to use )

I love the idea of software meters ,

No one wants to walk around with a meter doing photography... even pros . They would rather meter light by feel plus cameras metering.

there was a startup that made a iphone case with a diffuser cup idk if thats still around but might be a cool idea for dev to make a standardized case with diffuser (back) that can be easily removed..

All around tho nice piece of software

Developer Response ,

Hi Dasistgass,

Thank you for your review and feedback!

I understand. Please mind that our app is not developed for film photography usage but for gardening applications. Therefore, the measurement is specifically adapted for highest accuracy on common indoor farming grow lights. Additionally, we highly recommend to use a diffuser as advised within the app. I think this would solve your issue.

The camera exposure settings / suggestions you are mentioning are definitely something to think about for the future.

Again, thank you very much and best regards,
Dominik and the Korona Team

vitvorg ,

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.

Developer Response ,

Thank you very much for your kind and useful review! We will definitely consider the background image hold for a future release!

Funmcfunster ,

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.

Developer Response ,

Hi Funmcfunster,

Thank you very much for your review! We greatly appreciate your insight and are happy that you get good use of our app!

Best regards,

App Privacy

The developer, Lightray Innovation GmbH, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy.

Data Not Linked to You

The following data may be collected but it is not linked to your identity:

  • Usage Data
  • Diagnostics

Privacy practices may vary, for example, based on the features you use or your age. Learn More


  • Family Sharing

    With Family Sharing set up, up to six family members can use this app.

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