This converter turns atmospheres into inches of mercury instantly, using the exact factor 1 atmosphere = 29.9212524 inches 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. US aviation and weather altimeter setting unit.
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
29.9212524- The exact number of inches of mercury in one atmosphere
inches 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 29.9212524, the exact conversion factor.
- The result is displayed in inches 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 29.921252. That gives 149.6063 inches of mercury. A quick sanity check: one atmosphere is larger than one inch of mercury, so the number should get bigger — and it does.
Converting 72 atmospheres
72 × 29.921252 = 2,154.33 inches of mercury. Working backwards, 2,154.33 ÷ 29.921252 returns 72 atmospheres, which confirms the factor is applied the right way round.
How to read your score
Frequently asked questions
How many inches of mercury are in one atmosphere?
Exactly 29.9212524. 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 inches of mercury?
Inches Of Mercury = atmospheres × 29.9212524. To reverse it, divide instead: atmospheres = inches of mercury ÷ 29.9212524, which is the same as multiplying by 0.03342106094.
Is the atmosphere bigger than the inch of mercury?
Yes. One atmosphere equals 29.9213 inches of mercury, so it is the larger unit.
Why does my answer differ slightly from other atmospheres to inhg 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 inch of mercury?
US aviation and weather altimeter setting unit.
Atmospheres to inches of mercury reference table
| Atmospheres | Inches Of Mercury |
|---|---|
| 0.5 atm | 14.9606 inHg |
| 1 atm | 29.9213 inHg |
| 2 atm | 59.8425 inHg |
| 3 atm | 89.7638 inHg |
| 5 atm | 149.6063 inHg |
| 10 atm | 299.2125 inHg |
| 15 atm | 448.8188 inHg |
| 20 atm | 598.425 inHg |
| 25 atm | 748.0313 inHg |
| 50 atm | 1,496.06 inHg |
| 75 atm | 2,244.09 inHg |
| 100 atm | 2,992.13 inHg |
| 250 atm | 7,480.31 inHg |
| 500 atm | 14,960.63 inHg |
| 1000 atm | 29,921.25 inHg |
Exact factor: 1 atmosphere = 29.9212524 inches of mercury. Values rounded for display.