What this calculator does
RMS speed of gas molecules works out root-mean-square speed of molecules in an ideal gas from temperature and molar mass. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
Formulav_rms = √(3RT/M), R = 8.314462618 J/(mol·K) (CODATA)
The inputs explained
| Field | What to enter |
|---|---|
| Temperature (K) | A number, measured in K. Starts at 293.15. |
| Molar mass (air ≈ 28.97) (g/mol) | A number, measured in g/mol. Starts at 28.97. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the answer changes with temperature
Every other input is held at the calculator’s starting values while temperature varies. Select any row to load that scenario into the calculator.
How the answer changes with temperature