Inches of Mercury to Atmospheres
Convert inches of mercury to atmospheres instantly. 1 inHg = 0.0334210609 atm. Includes the exact factor, a conversion table of common values and the definition of both units.
How to convert inches of mercury to atmospheres
To convert inches of mercury to atmospheres, divide by 29.9212524019 (multiply by 0.0334210609). The relationship is fixed, so the same factor works for any quantity — there is nothing to look up and nothing that changes with temperature, location or context.
atm = inHg × 0.0334210609
Inches of Mercury to Atmospheres conversion table
The values people look up most often, rounded for reading. Use the calculator above for anything in between.
| 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 |
| 20 inHg | 0.668421 atm |
| 25 inHg | 0.835527 atm |
| 50 inHg | 1.671053 atm |
| 100 inHg | 3.342106 atm |
| 500 inHg | 16.71053 atm |
| 1,000 inHg | 33.421061 atm |
What is a inches of mercury?
The aviation altimeter unit: 29.92 inHg is standard sea-level pressure.
What is a atmosphere?
The standard atmosphere, defined as exactly 101,325 Pa.
The formula
atm = inHg × 0.0334210609
Every result on this page comes from this formula. Nothing is rounded until the final display, so figures match a spreadsheet to the cent.
How to use the Inches of Mercury to Atmospheres
- Type the number of inches of mercury you want to convert.
- Read the result in atmospheres straight away — there is no button to press.
- Check the table below for the values that come up most often, or reverse the conversion with the linked atmospheres to inches of mercury page.
Inches of Mercury to Atmospheres — frequently asked questions
How many atmospheres are in a inches of mercury?
One inches of mercury equals 0.0334210609 atm. atm = inHg × 0.0334210609
What is the formula to convert inches of mercury to atmospheres?
The formula is atm = inHg × 0.0334210609. It is an exact definition rather than an approximation, so the conversion never drifts no matter how large the number.
How do I convert atmospheres back to inches of mercury?
Divide instead of multiplying: one atmosphere is 29.9212524019 inHg. The reverse converter is linked in the related tools list.
Is this conversion exact?
Yes. Both units are defined against the same base unit by international agreement, so the factor is exact — any rounding you see is only in the display, which you can widen by entering more decimal places.
Is this inches of mercury to atmospheres free to use?
Yes. Every calculator on the site is free, needs no sign-up, and runs entirely in your browser, so your figures never leave your device.
What people search for
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About this calculator
Written and reviewed by The Samsung Calculator editorial team. Every calculator is written against a published formula, reviewed against at least one independent reference implementation, and dated when it changes.
Last reviewed August 19, 2026 · Calculation runs client-side · No data collected · Report an error