How many atm is 1 inHg?

1 inch of mercury (inHg) equals approximately 0.033421 standard atmospheres (atm). The precise factor is 1 inHg = 3.38639 × 10⁻² atm.

What is a standard atmosphere (atm)?

A standard atmosphere (atm) is defined as exactly 101,325 pascals. It represents average sea-level air pressure and is widely used in chemistry, physics, and engineering.

What is inHg used for?

Inches of mercury (inHg) is commonly used in meteorology and aviation in the United States. Barometric pressure and altimeter settings are typically reported in inHg.

Is standard sea-level pressure 29.92 inHg?

Yes. Standard sea-level pressure is 29.92 inHg, which equals exactly 1 atm (101,325 Pa). This is the reference point used in aviation and weather reporting.

How do I convert atm back to inHg?

Multiply the atm value by 29.9213 to get inHg. For example, 2 atm = 2 × 29.9213 = 59.84 inHg. Use the swap button on this converter to reverse the direction.

inHg to Atmospheres Converter

Name: inHg to Atmospheres Converter
Availability: InStock
Author: Nham Vu

Enter a pressure in inches of mercury (inHg) and get the equivalent value in standard atmospheres (atm) instantly.

Pressure Converter

Inches of Mercury (inHg)

Standard Atmospheres (atm)

Conversion Reference

Exact Factor

1 inHg = 0.0334211 atm

1 atm = 29.9213 inHg

inHg	atm
1	0.033421
5	0.167106
10	0.334211
29.92	1.000 (sea level)
50	1.671
100	3.342
1000	33.421

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Summary

Enter a pressure in inches of mercury (inHg) and get the equivalent value in standard atmospheres (atm) instantly.

How it works

Enter a pressure value in inches of mercury (inHg) in the input field.
The converter applies the factor: 1 inHg = 0.0334211 atm.
The result in standard atmospheres (atm) appears immediately.
Use the swap button to reverse the conversion (atm to inHg).
Copy the result with one click for use in calculations or reports.

Use cases

Convert barometric pressure readings from weather stations to atmospheres.
Cross-check altimeter settings (ALTIMETER) in aviation from inHg to atm.
Translate pressure data between US and metric scientific references.
Verify vacuum pump specs expressed in inHg against atm thresholds.
Convert historical weather records that use inHg into standard atm.
Check HVAC system pressures reported in inHg against spec limits in atm.

Frequently Asked Questions

Last updated: 2026-07-23 · Reviewed by Nham Vu