This converter turns atmospheres into millimeters of mercury instantly, using the exact factor 1 atmosphere = 759.9998917 millimeters of mercury. Type any number and the result updates as you go — nothing is sent to a server, so the arithmetic happens entirely in your browser.
Standard atmospheric pressure by definition — 101,325 pascals exactly. The clinical unit for blood pressure worldwide.
Because the relationship is a simple proportion, one multiplication does the whole job. The table further down gives pre-computed values for the amounts people look up most often, and the result panel also reports the reverse conversion so you can check the figure both ways.
The formula
atmospheres- The amount you are converting, measured in atmospheres
759.9998917- The exact number of millimeters of mercury in one atmosphere
millimeters of mercury- The converted result
How it works, step by step
- Enter the number of atmospheres you want to convert.
- The value is multiplied by 759.9998917, the exact conversion factor.
- The result is displayed in millimeters of mercury, rounded for readability.
- The unrounded value and the reverse conversion appear underneath so you can verify it.
Worked examples
Converting 5 atmospheres
Multiply 5 by 759.99989. That gives 3,800 millimeters of mercury. A quick sanity check: one atmosphere is larger than one millimeter of mercury, so the number should get bigger — and it does.
Converting 72 atmospheres
72 × 759.99989 = 54,719.99 millimeters of mercury. Working backwards, 54,719.99 ÷ 759.99989 returns 72 atmospheres, which confirms the factor is applied the right way round.
How to read your score
Frequently asked questions
How many millimeters of mercury are in one atmosphere?
Exactly 759.9998917. Every conversion on this page is that single number multiplied by your input, so the result carries no rounding error beyond what is shown.
What is the formula to convert atmospheres to millimeters of mercury?
Millimeters Of Mercury = atmospheres × 759.9998917. To reverse it, divide instead: atmospheres = millimeters of mercury ÷ 759.9998917, which is the same as multiplying by 0.001315789661.
Is the atmosphere bigger than the millimeter of mercury?
Yes. One atmosphere equals 760 millimeters of mercury, so it is the larger unit.
Why does my answer differ slightly from other atmospheres to mmhg converters?
Most differences come from rounding the factor too early. This tool keeps full double precision through the calculation and only rounds at the final display step, and it also shows the unrounded value so you can see exactly where any difference appears.
What is a atmosphere?
Standard atmospheric pressure by definition — 101,325 pascals exactly.
What is a millimeter of mercury?
The clinical unit for blood pressure worldwide.
Atmospheres to millimeters of mercury reference table
| Atmospheres | Millimeters Of Mercury |
|---|---|
| 0.5 atm | 379.9999 mmHg |
| 1 atm | 759.9999 mmHg |
| 2 atm | 1,520 mmHg |
| 3 atm | 2,280 mmHg |
| 5 atm | 3,800 mmHg |
| 10 atm | 7,600 mmHg |
| 15 atm | 11,400 mmHg |
| 20 atm | 15,200 mmHg |
| 25 atm | 19,000 mmHg |
| 50 atm | 37,999.99 mmHg |
| 75 atm | 56,999.99 mmHg |
| 100 atm | 75,999.99 mmHg |
| 250 atm | 189,999.97 mmHg |
| 500 atm | 379,999.95 mmHg |
| 1000 atm | 759,999.89 mmHg |
Exact factor: 1 atmosphere = 759.9998917 millimeters of mercury. Values rounded for display.