Inches Of Mercury to Atmospheres
Type a value in either box to convert between inches of mercury and atmospheres. The factor is 0.0334211.
| Inches Of Mercury | Atmospheres |
|---|---|
| 1 inHg | 0.033421 atm |
| 2 inHg | 0.066842 atm |
| 3 inHg | 0.100263 atm |
| 5 inHg | 0.167105 atm |
| 10 inHg | 0.334211 atm |
| 25 inHg | 0.835527 atm |
| 50 inHg | 1.671053 atm |
| 100 inHg | 3.342106 atm |
How to use
- Enter a value in the Inches Of Mercury field.
- The Atmospheres figure appears immediately — no button to press.
- Typing in the Atmospheres field converts back to Inches Of Mercury the same way.
- Use the reference table for the values that come up most often.
Inches Of Mercury to Atmospheres formula
The factor from inches of mercury to atmospheres is 0.0334210609.
atm = inHg × 0.0334210609
Why this factor: the inch of mercury and the atmosphere are both defined against the pascal, so dividing one definition by the other gives 0.0334210609 directly. Both definitions are set out in full below.
To go the other way, divide by 0.0334210609 — or use the Atmospheres to Inches Of Mercury converter, which is the same calculation reversed.
Worked example
Take 32 inHg and multiply by the factor 0.0334210609: the result is 1.069474 atm.
32 inHg × 0.0334210609 = 1.069474 atm
The converter above does this for any value you type, in either direction.
What is an inch of mercury?
An inch of mercury is the pressure of a one-inch mercury column, used for US barometric pressure.
Definition: About 3,386.389 pascals.
Where it is used: US weather barometric pressure, aircraft altimeter settings, and engine vacuum readings.
What is an atmosphere?
A standard atmosphere is a fixed reference pressure, originally average sea-level air pressure.
Definition: Defined as exactly 101,325 pascals — an exact convention, not a measurement.
Where it is used: Chemistry reference conditions, diving pressure, and high-pressure physics.
Inches Of Mercury vs Atmospheres
The inch of mercury is a US customary unit while the atmosphere is a specialized unit. That is why the factor between them is not a round number: the two systems were defined independently and only later tied together by exact agreement.
Frequently asked questions
How many atmospheres are in an inch of mercury?
One inch of mercury equals 0.0334210609 atmospheres.
What is the formula to convert inches of mercury to atmospheres?
Multiply the number of inches of mercury by 0.0334210609. To reverse it, divide by 0.0334210609 instead.
How do I convert atmospheres back to inches of mercury?
Divide by 0.0334210609, which is the same as multiplying by 29.9212524.
How many atmospheres are in 10 inches of mercury?
10 inHg works out to 0.334211 atm.
How is the inch of mercury defined?
About 3,386.389 pascals.