How many kPa is 1 inHg?

1 inch of mercury equals 3.386389 kPa. This is based on the conventional value of mercury density at 0 °C (32 °F), as defined by the World Meteorological Organization.

What is standard atmospheric pressure in inHg and kPa?

Standard atmosphere is 29.921 inHg, which equals 101.325 kPa. This is the reference used in aviation (altimeter setting) and as the baseline for many pressure specifications.

Why does HVAC use inHg?

In the United States, HVAC and ventilation systems traditionally express low static pressures (duct pressure, filter resistance) in inches of water column (inWC) or inches of mercury. The rest of the world uses Pascals (Pa) or kPa.

Is inHg the same as mmHg?

No. Millimeters of mercury (mmHg) is a smaller unit. 1 inHg = 25.4 mmHg. mmHg is common in medicine (blood pressure), while inHg is used in meteorology and aviation in the US.

How do I convert kPa back to inHg?

Divide the kPa value by 3.386389. For example, 101.325 kPa ÷ 3.386389 = 29.921 inHg. The Swap button on this page does this automatically.

inHg to Kilopascals Converter

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

Convert inches of mercury (inHg) to kilopascals (kPa) instantly — with a formula reference and a quick reverse lookup.

Convert Pressure

Inches of Mercury (inHg)

Kilopascals (kPa)

Quick Reference

Click any row to load that value.

Description	inHg	kPa
Standard atmosphere	29.921	101.325
Typical sea-level pressure	29.92	101.29
Low pressure storm	27.00	91.43
1 inHg (unit reference)	1.00	3.386
HVAC typical duct static	0.50	1.693

Formula

kPa = inHg × 3.386389

inHg = kPa ÷ 3.386389

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Summary

Convert inches of mercury (inHg) to kilopascals (kPa) instantly — with a formula reference and a quick reverse lookup.

How it works

Enter a pressure value in inches of mercury (inHg).
The converter multiplies the value by 3.386389 to get kilopascals.
The result and the full formula are shown immediately.
Use the Swap button to reverse-convert kPa back to inHg.
Common reference values (standard atmosphere, typical HVAC ranges) are shown below for quick sanity checks.

Use cases

Converting US weather barometric readings (e.g., 29.92 inHg) to kPa for international reports.
HVAC engineers converting duct static pressure specs from inHg to kPa.
Aviation students converting altimeter settings between US and ICAO formats.
Lab technicians normalizing pressure sensor readings to SI units.
Students verifying pressure unit conversions for physics or engineering coursework.

Frequently Asked Questions

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