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CO₂ Grow Room Calculator

Created by Julia Żuławińska
Reviewed by Łucja Zaborowska, MD, PhD candidate and Adena Benn
Last updated: Jan 18, 2024

Find out how much CO2 to add to a grow room with our CO2 grow room calculator! Read on to learn the optimum CO2 level for plant growth and how to calculate the CO2 flow rate of a tank to reach that level. But first, let's answer the most critical question: why would you add CO2 to a grow room?

As you may or may not know, plants perform photosynthesis, transforming carbon dioxide, water, and sunlight into oxygen and compounds they use to grow. While we have plenty of CO2 in the atmosphere (around 420 ppm), adding more CO2 may be beneficial if you care about yield. However, adding CO2 alone won't do much. You also need to provide enough nutrients, water, and light. Even if you add plenty of CO2, the amount of light can be a limiting factor if it's not intense enough, and the CO2 will go to waste.

🙋 You should also check out our potting soil calculator to find out how much soil you need for your containers.

How much CO₂ to add to a grow room?

To calculate the volume of CO2 for a grow tent, you need to know the following:

  • The dimensions or volume of the room/tent, and
  • The current and desired CO2 levels in parts per million (ppm).

Then you can use the following formula to find how much CO2 you need to add to your grow room:

CO2 needed=(CO2 targetCO2 current)106Vroom,\scriptsize \text{CO}_{2\text{ needed}} \!=\! \frac{(\text{CO}_{2\text{ target}} \!- \!\text{CO}_{2\text{ current}})}{10^6} \!\cdot \!\text{V}_{\text{room}},


  • Target and current CO2 levels should be expressed in ppm; and
  • The unit of the needed CO2 is the same as the one you used to express the room volume (Vroom\footnotesize \text{V}_{\text{room}}).

Based on the calculated volume of CO2, you can also find what should be the CO2 flow rate from a tank:

flowRate=CO2 neededtime\scriptsize \text{flowRate} = \frac{\text{CO}_{2\text{ needed}}}{\text{time}}

🙋 Now that you know how to calculate how much CO2 to add to a grow room, check out how much fertilizer you should add with our water soluble fertilizer calculator.

How to use the CO₂ grow room calculator?

Here's how to use the CO₂ grow room calculator:

  1. Input the grow room's or tent's dimensions or, if you know it, the room's volume.

  2. Type in the current CO2 level in your grow room. The atmospheric CO2 is typically around 420 ppm.

  3. Type in the desired CO2 level.

  4. Input the time the CO2 will be on.

  5. The CO2 grow room calculator will tell you how much CO2 you need to add to your grow room and what should be the CO2 flow rate. If the flow rate is too high, increase the tank's open time.

❗ While a high concentration of CO2 can be good for your plants, it can be dangerous for you. If you're adding CO2 to a grow room, don't stay there too long, or turn it down while you're there. If the CO2 concentration doesn't exceed 5000 ppm, you should be safe, but you can still notice symptoms like decreased concentration, headaches, dizziness, etc. Learn more in the CO₂ breathing emission calculator.


Should I add CO₂ to my grow room?

You don't have to add CO2 to a grow room. However, if you care about plant yield and have already tried other methods influencing growth, adding CO2 is an excellent next step.

What is the optimal CO₂ level for plant growth?

The optimal CO2 concentration for plant growth is 1200 to 1500 ppm. However, a high CO2 concentration won't affect plant growth if you don't also provide enough nutrients, water, and light.

Can you add too much CO₂ to a grow room?

In short – yes, you can for several reasons:

  1. You don't provide enough light for your plants, so adding more CO2 doesn't affect growth.
  2. Adding too much is toxic – don't exceed 1500 ppm, as it might result in plant damage.
  3. Don't add CO2 at night! At night, no photosynthesis occurs, so there's no need for CO2 supplementation.

How much CO₂ do I need if my grow room is 70 cubic feet?

You need about 0.05-0.07 cubic feet of CO2 (1.5-2 liters). The exact number depends on the ambient and target CO2 level. The higher the final level of CO2, the more you need. Find the exact volume of CO2 you need with the CO2 grow room calculator.

Julia Żuławińska
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