Growing plants is not only about watering and using food, but the light is the most important thing, so the plant needs exactly the right amount of light to be strong and give a good harvest, because too much or too little light is bad.
You need expensive professional tools like PAR Meters, but for a normal person or a beginner, the light meter app for plants is a great and very cheap start because it can change your phone into a simple meter.
Why Do We Need to Measure Light?
Not Enough Light
What happens: The plant grows very tall, and its stem becomes thin, and the leaves look pale, so the plant uses all its energy to make the stem longer instead of growing a nice, thick top.
The result: The plant is weak and sickly, and it can get sick easily, so it will not give a good harvest or flowers.
Too Much Light
What happens: The leaves become pale, look white, or get a yellow color, especially right under the lamp, and the sides of the leaves can become dry and brown, so the plant might close its stomata to "rest" from the light, which makes its growth slow.
The result: The leaves are damaged, the growth stops, and the plant uses energy to fix itself instead of making flowers.
How Do the Light Measuring Apps Work?
Your phone was not made for growing things, but it has small light sensors, which are usually the front camera or a sensor near it, and these sensors check the brightness, so the apps change this check into the unit lux ().
Lux is the way to measure brightness that a person's eye sees.
The main problem is: A Lux Meter sees green light the best which plants throw away, but it sees blue and red light badly which plants use to absorb a lot.
Top 10 Phone Apps to Check Plant Light (2025)
App Name | Main Function | General Rating |
AI Plant Finder | Full plant check and light score using AI | ⭐⭐⭐⭐⭐ |
Photone | The best way to change Lux to PPFD | ⭐⭐⭐⭐ |
Lux Light Meter Pro | Simple and clean Lux meter for home use | ⭐⭐⭐⭐ |
Planta: Plant & Garden Care | Light check with tips for specific home plants | ⭐⭐⭐⭐ |
Grow Light Meter | Special tool to check DLI | ⭐⭐⭐ |
PictureThis | Gives tips on caring for the plant as a whole.Lux meter that saves your checks | ⭐⭐⭐ |
LSP.evo | Tool that focuses on sunlight and how strong it is | ⭐⭐⭐ |
Light Meter by My-Plants | Simple app with a very small but clear screen | ⭐⭐⭐ |
Arboreal Light Meter | Made for forest work, but good for very low light checks | ⭐⭐ |
Dominant λ Light Spectrometer | Tries to show the light's colors, not just the brightness | ⭐⭐ |
AI Plant Finder
Pros
This app gives you full help because it finds sickness, helps with watering, and gives general advice about plant care, so it is a full helper.
It is very easy for new growers to use because the screen is simple and you do not need much science knowledge.
The app uses AI to change the numbers and gives you special advice based on what kind of plant you have.
Cons
The main check is in Lux, so you must trust the AI's math to change Lux into information that is good for your plant.
Photone
Pros
It has the best change of numbers because you can choose the type of your lamp (LED, HPS, Sun) to correctly change Lux to PPFD.
It shows special numbers like PPFD and DLI which professional people use to know how big the harvest will be.
This app has been shown to be very close to real PAR Meters when you set it up correctly.
Cons
You need to set it up well because for the best number, you must use a special paper or thing to make the light spread out on the camera.
It can be difficult for a person new to this because it has many settings and numbers to understand.
You must pay for some things because access to the change for all types of LED lamps often costs money.
Lux Light Meter Pro
Pros
It checks the Lux cleanly because it works well and gives you the most simple measure of brightness.
It has many features because it can save data, show the smallest/biggest numbers, and remember history.
It is good for work or home light checks because it is very good for checking the brightness that a person needs.
Cons
It is not for plant lights because it is completely wrong for pink LED lamps since it makes their numbers look very small.
It does not show PPFD because it only shows brightness and not the "food for the plants."
The number can be different because it depends on how good the sensor in your phone is.
Planta: Plant & Garden Care
Pros
It uses simple groups because it changes the numbers into easy zones like "low," "medium," or "high" light, which is easy to see.
It gives advice about types because it often has built-in tips about the light needed for popular house plants.
It shows pictures because it uses bars and colors that easily show where the plant is in the light zone.
Cons
The check is very rough because it is not good for growing professionally or in grow boxes.
It has no special settings because it does not try to change the number for different light colors, only general brightness.
Grow Light Meter
Pros
It checks DLI because it can find the DLI (total light amount for the day), which is the most important number for the harvest size.
It has special modes because it knows about the time the light is on (like 18 hours on and 6 hours off) for correct math.
It is good for special lamps because it works better for LED and HPS lamps than normal lux meters.
Cons
It needs knowledge because to use DLI, you must know the correct DLI numbers your plant needs at that time.
It has a small use because it is not good for checking the light from a window.
PictureThis
Pros
It saves checks because it lets you save and compare the numbers from different places at different times.
It is reliable because it uses well-known methods that are used in the photo world.
It has a simple look because the screen is clean and has few things on it.
Cons
It is only Lux because it has no way to change the number to PPFD or DLI.
It focuses on the camera because it often uses the main camera to check the light, which can be difficult to hold.
LSP.evo
Pros
It is good for the sun because it is easy to check windows, balconies, and greenhouses.
It is fast to start because you do not need to sign up or change many settings.
It gives simple advice because it often gives clear tips on the best place to put the plant near a window.
Cons
It is not good for lamps because it works very badly with fake light, especially LED lights that only use a few colors.
It has no extra features because it only checks the basic brightness.
Light Meter by My-Plants
Pros
It is very simple because the screen is clear and has no extra buttons.
It is free because the main things you need are usually free to use.
Cons
It is not very exact because it uses the simplest math and its number depends much on the phone sensor.
It has limits because it is only good for the most general checks and comparisons.
Arboreal Light Meter
Pros
It checks low light well because it measures light well in very dark places or deep inside the plant's leaves.
It helps with area because it can help guess the percentage of shadow, which is good for gardening outside.
Cons
It is for special use because it is not made for strong fake light.
It does not show DLI or PPFD because it focuses on percentages and Lux.
Dominant λ Light Spectrometer
Pros
It shows a picture of the colors because it helps you see if your lamp has a lot of blue or red.
It helps for looking at light quality because it gives an idea about the light's color quality, not just how much light there is.
Cons
It is very wrong because the numbers for colors using the phone sensor are not true and can be very wrong.
It works slowly because it needs more time to look at the data.
How to See if Your Plant is Happy
Short and strong growth: The plant is short and low to the ground, and the space between the leaves is very small, so the stem is thick and strong, which means the plant does not use energy to grow long.
Dark green leaves: The leaves have a deep, healthy green color, and they look thick because they have a lot of chlorophyll to catch the light.
Leaves look up: Many plant leaves "reach" for the light, making a "cup" or "hands" towards the lamp, which is a sign of good light work.
Strong side growth: The plant makes many side parts, which makes the plant look full and bushy.
Signs of Worry
A. Not Enough Light
Growing long: The plant looks thin and long, and the space between the leaves is very big, so the plant is trying to "reach" the light.
Pale leaves: The leaves become thin and light green or yellow, especially the old ones, because the plant does not have enough energy to make chlorophyll.
Dropping lower leaves: The plant "turns off" the old, lower leaves because they do not get light and only use its food.
B. Too Much Light
"Praying" or twisting: The leaves twist strongly inwards or fold up along the middle line, because they are trying to hide from the too-strong light.
Losing color: The leaves right under the lamp start to look white or yellow, or get a reddish/purple color, which means the chlorophyll is broken.