mmHg to Atmospheres Converter

mmHg to Atmospheres

Convert mmhg (mmHg) to atmospheres (atm). Both measure force per area, and the conversion comes up in weather, automotive, diving work.

The Formula

`` atmospheres = mmhg × 0.00131578966114 mmhg = atmospheres × 759.999891726 `

One mmhg is 0.001316 atmospheres, and one atmosphere is 759.9999 mmhg.

Conversion Table

mmHg	Atmospheres
1 mmHg	0.001316 atm
2 mmHg	0.002632 atm
5 mmHg	0.006579 atm
10 mmHg	0.013158 atm
25 mmHg	0.032895 atm
50 mmHg	0.065789 atm
100 mmHg	0.131579 atm
500 mmHg	0.657895 atm
1,000 mmHg	1.3158 atm

The Other Direction

Atmospheres	mmHg
1 atm	759.9999 mmHg
2 atm	1,520 mmHg
5 atm	3,800 mmHg
10 atm	7,600 mmHg
25 atm	19,000 mmHg
50 atm	37,999.99 mmHg
100 atm	75,999.99 mmHg
500 atm	379,999.95 mmHg
1,000 atm	759,999.89 mmHg

What Each Unit Is

mmHg (mmHg) — the pressure of a one-millimetre column of mercury, or 133.322 pascals. From the mercury barometer; medicine kept it after physics moved to pascals.

Atmospheres (atm) — exactly 101,325 pascals, by definition. The mean air pressure at sea level, adopted as a reference standard.

A Sense of Scale

• Normal blood pressure is 120/80 mmHg
• Atmospheric pressure is 760 mmHg
• Pressure doubles at 10 m underwater
• Everest’s summit is about 0.33 atm

Precision

The factor 0.00131578966114 is rounded. For engineering work carry more digits than the table above, and round only at the end — rounding at each step compounds.

In Code

`javascript const mmHgToAtmosphere = (value) => value * 0.00131578966114; ``

Where This Conversion Comes Up

• Weather
• Automotive
• Diving
• Aviation
• HVAC

How Many Decimals Do You Need?

Rounding the factor costs accuracy, and how much depends on the factor. Converting 137 mmHg with the factor truncated at each decimal place:

Decimals kept	Factor	137 mmHg becomes	Error
0	0	0	100.0000%
1	0	0	100.0000%
2	0	0	100.0000%
3	0.001	0.137	24.0000%
4	0.0013	0.1781	1.2000%

A rule that holds for any conversion: round once, at the end. Rounding the factor and then multiplying compounds the error through every subsequent calculation, while carrying full precision and rounding the final answer does not.

The right number of significant figures is set by your input, not by the converter. If you measured mmhg to three significant figures, the answer in atmospheres is only good to three — writing more digits claims precision the measurement never had.

Other Conversions From mmHg

The same value in every other unit this converter supports for pressure:

From	To	Unit
1 mmHg	133.322 Pa	Pascals
1 mmHg	0.133322 kPa	Kilopascals
1 mmHg	0.00133322 bar	Bar
1 mmHg	0.0193368 psi	PSI

Chaining conversions works — mmhg to metres to feet gives the same answer as mmhg to feet — but each step rounds, so a chain of three conversions carries three roundings. Convert directly where a direct factor exists.