Henrys Law Solubility Calculator
How much gas dissolves in a liquid depends on how hard that gas presses on the surface. Henry's law makes this exact: at a fixed temperature, the dissolved concentration is directly proportional to the gas's partial pressure, with the proportionality set by a solubility constant unique to each gas-liquid pair. It explains carbonated drinks, the gas exchange in your lungs, and why divers must ascend slowly. This calculator multiplies the partial pressure by the Henry's law constant you supply and returns the dissolved gas concentration in moles per liter.
Henry's law formula
C = k_H * P
mmol/L = C * 1000
The dissolved concentration C is the product of the Henry's law solubility constant k_H and the gas partial pressure P. With k_H in moles per liter per atmosphere and P in atmospheres, C is in moles per liter. Multiply by 1,000 to express it in millimoles per liter.
Henry's law facts
- Dissolved gas concentration is proportional to partial pressure at fixed temperature.
- Gases are less soluble in warmer water, so the constant decreases with temperature.
- Carbonated drinks are bottled under high carbon dioxide pressure to dissolve more gas.
- The default constant approximates carbon dioxide in water near room temperature.
- The Henry's law constant is user-editable because it is empirical and system-specific.
Henry's law: frequently asked questions
What is Henry's law?
Henry's law states that the amount of a gas dissolved in a liquid is directly proportional to the partial pressure of that gas above the liquid, at constant temperature. Double the partial pressure and you double the dissolved concentration. It explains why a sealed carbonated drink holds dissolved gas that fizzes out when you open it.
What is the Henry's law formula?
In the solubility form, C = k_H * P, where C is the dissolved gas concentration, P is the partial pressure of the gas, and k_H is the Henry's law solubility constant for that gas-liquid pair at the given temperature. With k_H in moles per liter per atmosphere and P in atmospheres, C is in moles per liter.
What is the Henry's law constant?
The Henry's law constant relates dissolved concentration to gas pressure for a specific gas, solvent, and temperature. It depends strongly on temperature: gases are less soluble in warm water, so k_H falls as temperature rises. Because it is empirical and depends on the system, it is a user-editable input here.
Why is the constant a user-editable input?
The Henry's law constant is an experimentally measured value that differs for every gas-solvent pair and changes with temperature, so it cannot be hardcoded for a general calculator. Enter the value from a reliable reference table for your gas, solvent, and temperature, in moles per liter per atmosphere, to get the correct solubility.
What units does this calculator use?
Enter the gas partial pressure in atmospheres and the Henry's law solubility constant in moles per liter per atmosphere. The output dissolved concentration is in moles per liter. Keep the constant's units consistent with your pressure unit so the product gives concentration directly.
Official sources
- NIST Chemistry WebBook: Henry's law and solubility data.
- NOAA: Carbon cycle and gas exchange research.
Reviewed by the CalculatorHub team, edited by James Graham, 16 June 2026. See our methodology.