Henry's Law Calculator
How much gas dissolves in a liquid at a given partial pressure — Henry's law, behind carbonation, diving and dissolved oxygen.
C = kH × P.
How the henry's law calculator works
C = kH × P. The dissolved concentration is directly proportional to the partial pressure of that gas above the liquid.
It explains a fizzy drink: bottled at high CO₂ pressure, opening it drops the partial pressure to near zero and most of the dissolved gas leaves. It also explains decompression sickness — nitrogen dissolves under pressure at depth and comes out of solution if the ascent is too fast.
Formula: C = kH × P
Worked examples
| Inputs | Result | Note |
|---|---|---|
| Oxygen in water at air pressure | 0.0002717 | 8.7 mg/L — typical dissolved oxygen |
| CO₂ in a fizzy drink | 0.085 | 3.7 g/L |
| Once opened | 0.0000136 | almost nothing stays dissolved |
FAQFrequently asked questions
What is Henry's law?
The amount of a gas that dissolves in a liquid is proportional to that gas's partial pressure above it.
Why does a drink go flat?
Because opening it drops the CO₂ partial pressure from a few atmospheres to the 0.0004 atm of air. Almost all the dissolved gas is then unstable and leaves.
What is dissolved oxygen in a river?
About 8 to 9 mg/L when saturated at 25 °C. Below about 5 mg/L most fish are in trouble.
How does this relate to diving?
At depth, higher pressure dissolves more nitrogen in the blood. Ascending too fast drops the pressure faster than it can leave, and it bubbles — decompression sickness.
Does temperature matter?
Very much. Gas solubility falls as temperature rises, which is why warm water holds less oxygen and warm drinks go flat faster.
Where these figures come from
- IUPAC — Standard atomic weights (2021 conventional values) — the molar-mass table
- NIST — CODATA 2018 fundamental physical constants — Avogadro constant, gas constant, speed of light
- NIST Chemistry WebBook — thermochemical data
- National Institute of Standards and Technology — the US measurement and reference-data authority
Last checked: September 2026. Atomic masses are the IUPAC conventional values; constants are CODATA 2018; equations are the standard textbook forms.