mmHg to Atmospheres
Convert millimeter of mercury to atmosphere instantly — type a value and read the result, with the exact formula shown.
Reviewed by the CalcCafe editorial team · Last updated 1 July 2026 · How we test our tools
Example
1 mmHg = 0.00131579 atm, 5 mmHg = 0.006578948 atm, 10 mmHg = 0.0131579 atm.
Common conversions: millimeter of mercury to atmosphere
Quick reference for the mmHg → atm values you are most likely to need, computed with the exact factor the converter above uses. It includes the specific values people most often look up (760 mmHg, 745 mmHg, 700 mmHg, 20 mmHg, 750 mmHg).
| Millimeter of mercury (mmHg) | Atmosphere (atm) |
|---|
| 1 mmHg | 0.001316 atm |
| 2 mmHg | 0.002632 atm |
| 3 mmHg | 0.003947 atm |
| 5 mmHg | 0.006579 atm |
| 10 mmHg | 0.013158 atm |
| 15 mmHg | 0.019737 atm |
| 20 mmHg | 0.026316 atm |
| 25 mmHg | 0.032895 atm |
| 30 mmHg | 0.039474 atm |
| 40 mmHg | 0.052632 atm |
| 50 mmHg | 0.065789 atm |
| 60 mmHg | 0.078947 atm |
| 70 mmHg | 0.092105 atm |
| 75 mmHg | 0.098684 atm |
| 80 mmHg | 0.105263 atm |
| 90 mmHg | 0.118421 atm |
| 100 mmHg | 0.131579 atm |
| 150 mmHg | 0.197368 atm |
| 200 mmHg | 0.263158 atm |
| 250 mmHg | 0.328947 atm |
| 500 mmHg | 0.657895 atm |
| 600 mmHg | 0.789474 atm |
| 700 mmHg | 0.921053 atm |
| 720 mmHg | 0.947369 atm |
| 745 mmHg | 0.980263 atm |
| 750 mmHg | 0.986842 atm |
| 760 mmHg | 1 atm |
| 797 mmHg | 1.0487 atm |
| 1,000 mmHg | 1.3158 atm |
Atmosphere to Millimeter of mercury
| Atmosphere (atm) | Millimeter of mercury (mmHg) |
|---|
| 1 atm | 759.9999 mmHg |
| 5 atm | 3,800 mmHg |
| 10 atm | 7,600 mmHg |
| 50 atm | 37,999.99 mmHg |
| 100 atm | 75,999.99 mmHg |
How it works
Atmosphere = Millimeter of mercury × 0.00131579. Every value is converted through a single pascal base unit using internationally defined conversion factors, so any from/to pair stays consistent.
Good to know
Converting millimeters of mercury (mmHg) to atmospheres (atm) comes up most often in medicine, weather, and chemistry. Blood pressure cuffs, vacuum gauges, and barometers all report in mmHg, while gas-law problems, scuba and altitude charts, and many lab procedures prefer atmospheres because 1 atm represents a clean, physically meaningful baseline: average sea-level air pressure.
The two units come from very different traditions. The millimeter of mercury is a metric-flavored unit rooted in the old mercury-column barometer, where pressure was literally read off the height a column of mercury rose. The atmosphere is a reference unit, defined in 1954 as exactly 101,325 pascals. Because both ultimately tie back to pascals, the relationship is fixed: 760 mmHg = 1 atm by definition.
The handy rule of thumb is to divide by 760, or remember that each mmHg is just shy of 0.0013 atm. For quick mental math, 76 mmHg is about 0.1 atm, 380 mmHg is 0.5 atm, and a normal systolic blood pressure of 120 mmHg works out to roughly 0.16 atm.
A common precision trap is confusing mmHg with the torr. They are almost identical (1 torr = 1/760 atm exactly), but the modern mmHg is tied to mercury's density and gravity and differs by about one part in seven million, so for everyday work they are interchangeable but not formally equal. Also watch the direction of the factor: multiplying by 760 instead of dividing by it is the most frequent mistake, turning a small atm value into an impossibly large one.
Frequently asked questions
How do you convert millimeter of mercury to atmosphere?
Multiply the number of millimeter of mercurys by 0.00131579 to get atmospheres. For example, 1 mmHg = 0.00131579 atm.
What is 1 millimeter of mercury in atmospheres?
1 millimeter of mercury equals 0.00131579 atmospheres (1 mmHg = 0.00131579 atm).
How many millimeter of mercurys are in 1 atmosphere?
There are 759.9999 millimeter of mercurys in 1 atmosphere.
Is this converter free and private?
Yes. It runs entirely in your browser, so your inputs never leave your device, there is no sign-up, and it works offline once loaded.
Are the conversions exact?
Conversions use internationally defined factors and are exact where the definitions are exact (for example, 1 inch = 2.54 cm). Displayed results are rounded for readability.
People also ask
How many mmHg are in 1 atm?
Exactly 760 mmHg equal 1 atmosphere, since the atmosphere is defined as 760 millimeters of mercury (101,325 pascals).
What is 760 mmHg in atm?
760 mmHg equals exactly 1 atm. This is the standard sea-level reference pressure.
How do I convert mmHg to atm?
Divide the mmHg value by 760. For example, 380 mmHg / 760 = 0.5 atm, and 1520 mmHg / 760 = 2 atm.
What is normal blood pressure of 120 mmHg in atmospheres?
120 mmHg is about 0.158 atm (120 / 760). Note that blood pressure is measured as a gauge pressure above atmospheric, not an absolute value.
Is mmHg the same as torr?
Practically yes: 1 torr is exactly 1/760 atm, and modern mmHg differs by only about one part in seven million. For all everyday and most scientific purposes they are interchangeable.
What is 1 mmHg in atm?
1 mmHg equals about 0.00131579 atm (1 / 760). It is a very small fraction of an atmosphere.
How many atm is 500 mmHg?
500 mmHg is about 0.658 atm (500 / 760), which is roughly two-thirds of sea-level pressure.
Why is one atmosphere equal to 760 mmHg?
Because 1 atm is defined as 101,325 Pa, and that pressure supports a mercury column 760 mm tall under standard gravity and mercury density. The 760 figure is built into the definition.
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Sources & references
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