This converter turns inches of mercury into atmospheres instantly, using the exact factor 1 inch of mercury = 0.03342106094 atmospheres. Type any number and the result updates as you go — nothing is sent to a server, so the arithmetic happens entirely in your browser.
US aviation and weather altimeter setting unit. Standard atmospheric pressure by definition — 101,325 pascals exactly.
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
inches of mercury- The amount you are converting, measured in inches of mercury
0.03342106094- The exact number of atmospheres in one inch of mercury
atmospheres- The converted result
How it works, step by step
- Enter the number of inches of mercury you want to convert.
- The value is multiplied by 0.03342106094, the exact conversion factor.
- The result is displayed in atmospheres, rounded for readability.
- The unrounded value and the reverse conversion appear underneath so you can verify it.
Worked examples
Converting 5 inches of mercury
Multiply 5 by 0.033421061. That gives 0.167105 atmospheres. A quick sanity check: one inch of mercury is smaller than one atmosphere, so the number should get smaller — and it does.
Converting 72 inches of mercury
72 × 0.033421061 = 2.4063 atmospheres. Working backwards, 2.4063 ÷ 0.033421061 returns 72 inches of mercury, which confirms the factor is applied the right way round.
How to read your score
Frequently asked questions
How many atmospheres are in one inch of mercury?
Exactly 0.03342106094. 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 inches of mercury to atmospheres?
Atmospheres = inches of mercury × 0.03342106094. To reverse it, divide instead: inches of mercury = atmospheres ÷ 0.03342106094, which is the same as multiplying by 29.9212524.
Is the inch of mercury bigger than the atmosphere?
No. One inch of mercury is only 0.0334211 of a atmosphere, so the atmosphere is the larger unit.
Why does my answer differ slightly from other inhg to atmospheres 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 inch of mercury?
US aviation and weather altimeter setting unit.
What is a atmosphere?
Standard atmospheric pressure by definition — 101,325 pascals exactly.
Inches Of Mercury to atmospheres reference table
| Inches Of Mercury | Atmospheres |
|---|---|
| 0.5 inHg | 0.016711 atm |
| 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 |
| 15 inHg | 0.501316 atm |
| 20 inHg | 0.668421 atm |
| 25 inHg | 0.835527 atm |
| 50 inHg | 1.6711 atm |
| 75 inHg | 2.5066 atm |
| 100 inHg | 3.3421 atm |
| 250 inHg | 8.3553 atm |
| 500 inHg | 16.7105 atm |
| 1000 inHg | 33.4211 atm |
Exact factor: 1 inch of mercury = 0.03342106094 atmospheres. Values rounded for display.