Convert Inches of mercury to Atmospheres
1 inch of mercury is 0.033421 atm. One inch of mercury is exactly 0.0334210609425 atmospheres.
One inch of mercury is 0.033421061 atmospheres. To convert inches of mercury to atmospheres, multiply by 0.033421061; to go the other way, divide by 0.033421061 or multiply by 29.921252. The factor is exact rather than rounded: it follows from NIST Special Publication 811. The pressure of a one-inch column of mercury at 0 °C, fixed by convention at 3,386.389 pascals.
Factor checked against the defining standard · How we check
- Inches of mercury × 0.033421061
value * 0.03342106094250.033 atm
1 inch of mercury in every pressure unit
| Unit | Value | Exact factor |
|---|---|---|
| pounds per square inch | 0.4911541996 psi | × 0.491154199634 |
| bars | 0.03386389 bar | × 0.03386389 |
| pascals | 3,386.389 Pa | × 3,386.389 |
| kilopascals | 3.386389 kPa | × 3.386389 |
| megapascals | 0.003386389 MPa | × 0.003386389 |
| atmospheres | 0.03342106094 atm | × 0.0334210609425 |
| torr | 25.40000632 Torr | × 25.4000063163 |
| inches of mercury (as entered) | 1 inHg | — |
Factors are entered by hand from NIST Special Publication 811 rather than derived from a units library, so the ones that terminate are exact rather than rounded.
How do you convert inches of mercury to atmospheres?
- 1.Take the measurement in inches of mercury.
- 2.Multiply by 0.033421061 — that is how many atmospheres fit in one inch of mercury.
- 3.To go back the other way, divide by 0.033421061, or multiply by 29.921252.
Worked example: 25 inches of mercury to atmospheres
- Formula
- inHg × 0.033421061 = atm
- Arithmetic
- 25 × 0.033421061 = 0.835527 atm
- Answer
- 25 inHg = 0.835527 atm
The factor is rounded for display; the figure above is computed from the full value.
Inches of mercury to atmospheres conversion table
| Inches of mercury | Atmospheres |
|---|---|
| 1 inHg | 0.033421 atm |
| 2 inHg | 0.066842 atm |
| 3 inHg | 0.100263 atm |
| 4 inHg | 0.133684 atm |
| 5 inHg | 0.167105 atm |
| 6 inHg | 0.200526 atm |
| 7 inHg | 0.233947 atm |
| 8 inHg | 0.267368 atm |
| 9 inHg | 0.30079 atm |
| 10 inHg | 0.334211 atm |
| 12 inHg | 0.401053 atm |
| 15 inHg | 0.501316 atm |
| 20 inHg | 0.668421 atm |
| 25 inHg | 0.835527 atm |
| 50 inHg | 1.671053 atm |
| 100 inHg | 3.342106 atm |
| 200 inHg | 6.684212 atm |
| 300 inHg | 10.026318 atm |
| 500 inHg | 16.71053 atm |
| 1000 inHg | 33.421061 atm |
| 2000 inHg | 66.842122 atm |
| 5000 inHg | 167.105305 atm |
| 10000 inHg | 334.210609 atm |
What is an inch of mercury?
The pressure of a one-inch column of mercury at 0 °C, fixed by convention at 3,386.389 pascals. US aviation altimeters and barometers read in it.
What is a standard atmosphere?
Exactly 101,325 pascals by definition, not by measurement — it was fixed as a reference, and the real pressure outside your window is never precisely it.
How many atmospheres are in an inch of mercury?
One inch of mercury is 0.033421061 atmospheres. Going the other way, one standard atmosphere is 29.921252 inches of mercury. Both figures come from the same defined relation rather than from a measurement, which is why they are the same today as they were in 1959.
Every pressure unit here
| Unit | Symbol | One of these is |
|---|---|---|
| Pounds per square inch | psi | 6894.7573 pascal |
| Bars | bar | 100000 pascal |
| Pascals | Pa | the base unit |
| Kilopascals | kPa | 1000 pascal |
| Megapascals | MPa | 1000000 pascal |
| Atmospheres | atm | 101325 pascal |
| Torr | Torr | 133.32237 pascal |
| Inches of mercury | inHg | 3386.389 pascal |
Questions people actually ask
- How many atmospheres are in an inch of mercury?
- 0.033421061. Exactly 101,325 pascals by definition, not by measurement — it was fixed as a reference, and the real pressure outside your window is never precisely it.
- How do I convert atmospheres back to inches of mercury?
- Divide by 0.033421061, or multiply by 29.921252 — they are the same operation.
Other pressure conversions
Atmospheres to inches of mercury — the same conversion the other way.