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Calculates how much carbon dioxide a space needs to reach a target concentration, how long injection takes, what each fill costs, and how long a 20 lb tank lasts.
Room Dimensions
L (ft)
W
H
Target CO₂ (ppm)
1200Current CO₂ (ppm)
CO₂ Source
Flow Rate (CFH)
Air Exchanges/Hour
Room Volume
800 ft³
CO₂ Needed
0.64 ft³
33.3g
Injection Time
3.8 min
Cost Per Fill
$0.06
20lb Tank Lasts
272 fills
CO₂ Level
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Create Free Account →Plants use CO₂ as the carbon source for photosynthesis. Ambient air contains ~400 ppm CO₂, but most plants can utilize up to 1200-1500 ppm when light intensity is sufficient. Supplementing CO₂ can increase growth rates by 20-30%, but only when combined with strong lighting (DLI above 40 mol/m²/day) and proper environmental control.
Correction (1 September 2026): the 20 lb tank capacity constant was wrong (535 cubic feet, about three times the real figure), so the tank fills result read about three times too high. Capacity is now derived from the tank’s CO₂ mass and gas density (about 174 cubic feet at 20°C), and the strongest safety warning, above 2000 ppm, previously never shown, now displays. A calculation saved before this date still holds the older, inflated fills figure: re-run it to refresh.
What CO2 level is best for plants?
1000-1500 ppm is the sweet spot for most plants when combined with strong lighting. Above 1500 ppm, diminishing returns set in and safety risks increase. Ambient air is ~400 ppm.
Do I need a sealed room for CO2?
Yes, for maximum efficiency. In a ventilated room, CO2 escapes with each air exchange, requiring continuous replenishment. A sealed room with AC/dehumidifier is the most cost-effective approach.
Is CO2 dangerous?
Yes, at high concentrations. Above 1500 ppm causes headaches, above 5000 ppm is dangerous. Always use a CO2 monitor, and ventilate before entering a room with supplemental CO2.
When should I run CO2?
Only during lights-on hours when plants are photosynthesizing. CO2 during dark periods is wasted and accumulates dangerously. Use a timer synced to your light schedule.
Theme
Width
Height (px)
<iframe src="https://growmeridian.com/embed/co2-calculator" width="100%" height="500" frameborder="0" style="border-radius:12px;" title="co2 calculator"></iframe>
📡 Use via API
Access this calculator programmatically with our REST API
The calculator works from the volume of the space and the gap between the current and target concentration.
Concentration is in parts per million by volume (SI canonical: mol/m^3). Volume is in cubic feet, mass in grams, flow rate in cubic feet per hour, burner rating in BTU per hour.
Running the calculator at its own default inputs:
Inputs
Result
A sealed space needs one fill. Add air changes per hour and the calculator reports the continuous top-up a ventilated space needs instead.
| Concentration (ppm) | What it means |
|---|---|
| About 400 | Ambient outdoor air, the baseline the calculator starts from |
| 1,000 to 1,500 | The useful supplementation band when light is strong enough to match |
| Above 1,500 | Diminishing returns, and the point at which the calculator raises its safety warning: use a monitor, ventilate before entering, and never sleep in the space |
| Above 2,000 | The calculator raises its strongest warning: levels here cause headaches, dizziness, and impaired judgment, and are not recommended |
| 5,000 | The occupational exposure limit for an eight-hour working day |
| Constant | Value |
|---|---|
| CO2 density | 52.1 g per cubic foot (about 1.84 g per liter at 20 C and 1 atm) |
| 20 lb tank capacity | About 174 cubic feet of gas (9,072 g at 52.1 g per cubic foot) |
| Cost basis | $0.10 per cubic foot |
| Propane yield | 21.8 cubic feet of CO2 per lb |
| Propane per BTU | 0.0000455 lb |
| Condition | Guidance |
|---|---|
| Light level | DLI above 40 moles per square meter per day, or supplementation is wasted |
| Enclosure | Sealed rooms hold the charge; ventilated rooms need continuous replenishment |
| Timing | Lights-on hours only; CO2 in the dark period is wasted and accumulates |
| Monitoring | Use a CO2 monitor and ventilate before entering an enriched space |