CO2 Grow Room Calculator

Your details

Interior length of the grow space.
ft
Interior width of the grow space.
ft
Floor-to-ceiling height.
ft
Current CO2 concentration in the room before enrichment. Outdoor air is roughly 420 ppm.
ppm
Desired CO2 concentration. 1200-1500 ppm is optimal for most crops; never exceed 5000 ppm for human safety.
ppm
Sets a recommended target. Choose Custom to use your own ppm value.
How often fresh air replaces room air, in minutes. Sealed rooms use 60-120 min; ventilated rooms may be shorter.
min
CO2 output rate of your tank regulator or generator. Check the device label.
ft³/h
Weight of liquid CO2 in the cylinder. Common sizes: 5 lb, 10 lb, 20 lb (US); 2 kg, 5 kg, 10 kg (metric). Set to 0 to skip tank calculations.
lb
What you pay for a refill. Used to calculate cost per grow cycle.
USD
CO2 needed per cycleOptimal flowering range
0.553ft³

Volume of pure CO2 to raise the room from ambient to target

Room volume512ft³
CO2 needed (liters)15.7L
On-time per cycle2.2min
Cycles per tank316
Tank duration316h
Cost per cycle0.0791USD
Effective target ppm1,500ppm
1,500 ppm
Low<600Vegetative600-1000Optimal1000-1500High1500-2000Dangerous2000+

Your 512 ft³ grow room needs 0.553 ft³ of CO2 per cycle.

  • You need to raise CO2 by 1,080 ppm each cycle, requiring about 0.553 ft³ (15.7 L) of pure CO2.
  • Run your CO2 supply for approximately 2.2 minutes at the start of each enrichment cycle to reach the target concentration.
  • A full tank covers roughly 316 cycles (316.0 hours of light-period enrichment) before needing a refill.

Next stepMount the CO2 supply near the top of the room (CO2 is heavier than air and sinks). Pair with a CO2 controller or timer to automate dosing, and always run a safety sensor if people occupy the space.

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