Aquarium CO2 Calculator: CO2 ppm from KH & pH
Free aquarium CO2 calculator: enter KH and pH to get dissolved CO2 in ppm via 3 × KH × 10^(7−pH). Target 20-30 ppm for planted tanks.
Aquarium CO₂ Calculator (pH/KH)
Dissolved CO₂
19.0 ppm
Assessment
Low-moderate
Formula
CO₂ = 3 × KH × 10⁽⁷⁻ᵖᴴ⁾
ℹ️ The pH/KH method assumes carbonates are your only buffer — phosphate buffers, peat, or heavy organics make it read high. Cross-check with a drop checker (4 dKH solution turning green ≈ 30 ppm).