CO₂ Grow Room Calculator
Find out exactly how many grams (or litres) of CO₂ you need to inject into a sealed grow room to raise the concentration from ambient (~400 ppm) to your chosen target. Enter room dimensions and target ppm and get the mass and volume of CO₂ required.
m
m
m
ppm
ppm
Grams of pure CO₂ needed to raise the room from ambient to target concentration
- 1
Room volume
3 × 3 × 2.4 m = 21.6 m³ - 2
Concentration rise (ΔpCO₂)
1,200 − 400 ppm = 800 ppm - 3
CO₂ volume needed
21.6 × 800 × 10⁻⁶ = 0.01728 m³ppm = 10⁻⁶ m³ of CO₂ per m³ of air. - 4
CO₂ volume in litres
0.01728 × 1000 = 17.28 L - 5
CO₂ mass required
0.01728 m³ × 1965 g/m³ = 34 g
How does this calculator work?
CO₂ mass (g) = room volume (m³) × (target ppm − ambient ppm) × 10⁻⁶ × 1965. For a 3 m × 3 m × 2.4 m room raised from 400 to 1200 ppm, that is about 13.8 g of CO₂. Rooms are not perfectly sealed, so a continuous supply with a CO₂ controller is needed to sustain the target concentration.
Formula
How this is calculated
Plants photosynthesize more efficiently at CO₂ concentrations above the ambient ~400 ppm. Controlled-environment growers commonly target 1000–1500 ppm to accelerate growth; some push to 1500–2000 ppm for CO₂-tolerant crops. Above ~2000 ppm returns diminish and operator safety becomes a concern.
The calculation converts the ppm rise (parts per million by volume) to a fractional increase, multiplies by room volume to get the extra gas volume needed, then converts to mass using CO₂ density at standard conditions (1.965 kg/m³ at 0 °C, 1 atm). Real grow rooms aren't perfectly sealed — HVAC systems and plant respiration remove CO₂ continuously — so treat the result as the initial injection dose; a controller and regulator are needed for steady maintenance.
The 2024 ambient CO₂ level is approximately 420 ppm; the default of 400 ppm is a round conservative figure. Adjust it to your local or indoor baseline reading for a more precise top-up calculation.
Frequently asked questions
Most growers target 1000–1500 ppm. Photosynthesis accelerates noticeably above ~700 ppm and plateaus for most crops around 1500 ppm. Concentrations above 2000 ppm can cause plant stress and are a safety hazard for humans (OSHA limit is 5000 ppm over 8 hours).
This is the density of pure CO₂ gas at standard temperature and pressure (0 °C, 1 atm). At typical room temperature (~20 °C) the density is about 1.84 kg/m³, so the real mass needed is slightly less. Using STP is a safe, standard reference; adjust if high precision is required.
A single fill only works in a nearly sealed room. In practice you need a CO₂ tank with a regulator, a CO₂ controller and sensor, and timed injections to replace what is removed by ventilation and plant uptake. The calculator gives you the initial dose; your controller handles the ongoing top-up.
TG we-Calculate Editorial Team. (2026). CO₂ Grow Room Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/co2-grow-room-calculator
TG we-Calculate Editorial Team. "CO₂ Grow Room Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/co2-grow-room-calculator.
TG we-Calculate Editorial Team, "CO₂ Grow Room Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/co2-grow-room-calculator
@misc{wecalculate_co2_grow_room_calculator, title = {CO₂ Grow Room Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/co2-grow-room-calculator}}, year = {2026}, note = {TG we-Calculate} }
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