Millimeters of mercury at standard gravity.
mmHgs to Atmospheres Converter — mmHg to atm
Convert mmHg (mmHg) to Atmosphere (atm) using the exact conversion factor (1 mmhg = 0.0013157897 atmosphere). See the formula, worked examples, conversion table, and common uses.
mmHgs to Atmospheres converter
Converter
Pressure Converter
Convert pascals, bars, PSI, atmospheres, mercury columns, water columns, and engineering pressure units.
Context values
Some unit families need one extra value for a physically accurate result.
A standard atmosphere is exactly 101,325 pascals.
Result = input x 133.3223874 / 101325.
Pressure uses the pascal as the base unit.
Reserved above the conversion cards and below the converter.
About Converting mmHgs to Atmospheres
mmHg and Atmosphere both show up on pressure gauges — psi is standard on US tire and tool specifications, while bar is the everyday pressure unit across most of the rest of the world. Specifically: Millimeters of mercury at standard gravity, and a standard atmosphere is exactly 101,325 pascals.
Formula
atmospheres = mmhgs × 0.00131578966114
This factor comes from each unit's defined relationship to the category's base unit: 1 mmhg equals 133.322387415 base units, and 1 atmosphere equals 101325 base units, so dividing one by the other gives the direct mmhg-to-atmosphere factor of 0.00131578966114.
Simple example
1 mmHg × 0.001315789661 = 0.0013157897 atm
1 mmhg = 0.0013157897 atmospheres.
Real-world example
35 mmHg × 0.001315789661 = 0.0460526381 atm
35 mmhgs = 0.0460526381 atmospheres.
Conversion table
| mmHg (mmHg) | Atmosphere (atm) |
|---|---|
| 1 mmHg | 0.0013157897 atm |
| 5 mmHg | 0.0065789483 atm |
| 10 mmHg | 0.0131578966 atm |
| 25 mmHg | 0.0328947415 atm |
| 50 mmHg | 0.0657894831 atm |
| 100 mmHg | 0.1315789661 atm |
Reverse conversion: Atmosphere to mmHg
0.0013157897 atm × 759.9998917 = 1.00000003 mmHg
0.0013157897 atmospheres = 1.00000003 mmhgs.
mmhgs = atmospheres × 759.999891726
For a page dedicated to this direction, see Atmosphere to mmHg.
Understanding the mmHg (mmHg)
Millimeters of mercury at standard gravity.
Understanding the Atmosphere
Atmosphere (atm) measures pressure. Defined as exactly 101,325 pascals, originally based on the average atmospheric pressure at mean sea level. It is classified as a non-SI unit accepted for use with the SI.
Where it's used: Widely used internationally in chemistry, meteorology, and diving/aviation contexts alongside the pascal and bar
Uses of the Atmosphere today
- Chemistry (standard conditions are often defined at 1 atm)
- Diving and aviation pressure references
- General reference for everyday atmospheric pressure
Atmosphere — sources
- BIPM SI Brochure — Standard atmosphere listed among non-SI units with a fixed exact value in pascals.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many atmospheres are in 1 mmhg?
1 mmhg equals 0.0013157897 atmospheres, using the exact defined conversion factor rather than an estimate.
How do I convert mmhg to atmosphere?
Multiply the mmhg value by 0.001315789661. The converter above does this instantly to whatever precision you set.
How do I convert atmosphere back to mmhg?
Use the reverse factor: 1 atmosphere equals 759.9998917 mmhgs. You can also use the swap control in the converter above to flip the direction instantly.
What is a mmhg?
mmHg (mmHg) is a unit of pressure.
What is a atmosphere?
Atmosphere (atm) measures pressure. Defined as exactly 101,325 pascals, originally based on the average atmospheric pressure at mean sea level. It is classified as a non-SI unit accepted for use with the SI.
Is the mmhg to atmosphere conversion exact?
Yes. Defined as exactly 101,325 pascals, originally based on the average atmospheric pressure at mean sea level. That fixed definition is what the converter above uses, so any rounding you see is a display choice, not a limitation of the math.