How to Convert Atmospheres to Millimetres of mercury (atm to mmHg)
Pressure conversions are used for tyre pressure (psi or bar), blood pressure readings in mmHg and weather maps in millibars. This guide shows how to convert atmospheres into millimetres of mercury by hand, with examples and a quick-reference table.
The conversion
To convert atmospheres to millimetres of mercury, multiply the value by 760.0021001785. To go the other way, divide by the same number (or multiply by 0.0013157858). For a quick estimate, multiply by about 760.
Millimetres of mercury = atmospheres × 760.0021001785
Worked examples
- 3 atm = 2,280.01 mmHg
- 12.5 atm = 9,500.03 mmHg
- 75 atm = 57,000.16 mmHg
Atmospheres to Millimetres of mercury table
| Atmospheres | Millimetres of mercury |
|---|---|
| 1 atm | 760.0021 mmHg |
| 2 atm | 1,520 mmHg |
| 5 atm | 3,800.01 mmHg |
| 10 atm | 7,600.02 mmHg |
| 20 atm | 15,200.04 mmHg |
| 25 atm | 19,000.05 mmHg |
| 50 atm | 38,000.11 mmHg |
| 100 atm | 76,000.21 mmHg |
| 250 atm | 190,000.53 mmHg |
| 500 atm | 380,001.05 mmHg |
| 1,000 atm | 760,002.1 mmHg |
Common questions
Is atm to mmHg exact?
The factors used here are the internationally defined values where they exist; results are rounded for display only.
How do I convert back?
Use the Millimetres of mercury to Atmospheres converter.
Mistakes to avoid
Rounding the factor too early
Using 3 instead of 3.28 for feet per metre introduces an error of almost 9% before you have started.
Forgetting squared and cubed units
Area and volume factors are the length factor squared or cubed, so 1 m² is about 10.76 sq ft, not 3.28.
Multiplying when you should divide
Converting to a smaller unit gives a bigger number, and converting to a larger unit gives a smaller one. If your answer moves the wrong way, you have inverted the factor.
Background
Writing the units next to every number while you work is the simplest way to avoid mistakes. If the units do not cancel to leave the one you want, the calculation is set up wrongly.
A conversion table is handy for common values, but a calculator is faster and avoids interpolation errors for anything in between.
Unit conversion is simply multiplication by a fixed ratio. The ratio between two units of the same quantity never changes, so once you know it you can convert any value in either direction.
For any value, use the Atmospheres to Millimetres of mercury Converter or browse all pressure converters.
Run your own numbers: Atmospheres to Millimetres of mercury Converter