Fidamen

Convert Kilopascals to Inches of Mercury - Pressure Converter

This converter converts a pressure value expressed in kilopascals (kPa) to inches of mercury (inHg). The relationship is a fixed mathematical conversion when using the conventional definition of inHg tied to mercury column height under standard gravity.

Use this tool for everyday engineering, meteorological and HVAC work. For high-precision laboratory or legal metrology, read the accuracy caveats below and follow calibration and traceability guidance to NIST and relevant standards bodies.

Updated Nov 22, 2025QA PASS — golden 25 / edge 120Run golden-edge-2026-01-23

Governance

Record d2e01e52b511 • Reviewed by Fidamen Standards Committee

Interactive Converter

Convert between kilopascal and inch of mercury with precision rounding.

Quick reference table

KilopascalInch of Mercury
KPA 1.00 kPa0.2953 inHg
KPA 5.00 kPa1.4765 inHg
KPA 10.00 kPa2.953 inHg
KPA 25.00 kPa7.3825 inHg
KPA 50.00 kPa14.765 inHg
KPA 100.00 kPa29.53 inHg

Methodology

The conversion is performed using the conventional physical relation that 1 inHg equals 3386.389 pascals under standard conditions for mercury column definitions. The converter applies that established factor and reports results to a reasonable number of significant digits.

This conversion assumes standard gravity and the conventional mercury density implicit in the inHg definition. Temperature-dependent changes to the density of mercury cause slight variations; some industries use temperature-specified variants (for example, inHg at 60°F).

For regulatory, safety, and calibration contexts, ensure instruments are calibrated with traceability to national standards and comply with applicable standards from NIST, ISO, IEEE, and OSHA as relevant to your application.

Key takeaways

This converter applies the conventional fixed factor 1 inHg = 3386.389 Pa to convert kPa to inHg using inHg = kPa * 0.2952998307.

For routine work, the result is suitable; for metrology or regulatory uses, follow calibration, document uncertainty, and use temperature-corrected factors if required by your standard.

Worked examples

Example 1: 101.325 kPa → 101.325 * 0.2952998307 = 29.9213 inHg (standard atmospheric pressure).

Example 2: 50 kPa → 50 * 0.2952998307 = 14.76499 inHg (rounded to 14.765 inHg).

F.A.Q.

Is the conversion exact or does it depend on temperature?

The mathematical conversion using the conventional factor is fixed for the defined inHg unit. However, real-world mercury column measurements depend on mercury density, which varies slightly with temperature. Some applications define inHg at a specific temperature (for example, 60°F). For traceable metrology, use the temperature-corrected factor and document the reference conditions.

How many decimal places should I trust?

For general engineering and weather reporting, reporting 3 to 5 significant digits is usually sufficient. For laboratory or calibration work, specify uncertainty and follow the precision requirements of your standard or test method; do not rely solely on displayed digits without uncertainty assessment.

Do I need calibration traceable to a standards body?

Yes. When measurements affect safety, compliance, contracts, or legal evidence, instruments should be calibrated with traceability to national standards such as NIST and follow applicable ISO or IEEE standards. Keep calibration records and stated measurement uncertainty.

What is the difference between inHg variants (e.g., 0°C vs 60°F)?

Variants arise because mercury density changes with temperature and some conventions specify inHg at a reference temperature. The numeric difference is small but relevant for precise work. Confirm which variant your procedure, instrument, or standard requires.

Can I convert back from inHg to kPa with this tool?

Yes. The inverse conversion uses the reciprocal factor: kPa = inHg * 3.386389. Use the appropriate direction and note the same caveats about reference conditions and uncertainty.

Sources & citations

Further resources

Versioning & Change Control

Audit record (versions, QA runs, reviewer sign-off, and evidence).

Record ID: d2e01e52b511

What changed (latest)

v1.0.0 • 2025-11-22 • MINOR

Initial publication and governance baseline.

Why: Published with reviewed formulas, unit definitions, and UX controls.

Public QA status

PASS — golden 25 + edge 120

Last run: 2026-01-23 • Run: golden-edge-2026-01-23

Engine

v1.0.0

Data

Baseline (no external datasets)

Content

v1.0.0

UI

v1.0.0

Governance

Last updated: Nov 22, 2025

Reviewed by: Fidamen Standards Committee (Review board)

Credentials: Internal QA

Risk level: low

Reviewer profile (entity)

Fidamen Standards Committee

Review board

Internal QA

Entity ID: https://fidamen.com/reviewers/fidamen-standards-committee#person

Semantic versioning

  • MAJOR: Calculation outputs can change for the same inputs (formula, rounding policy, assumptions).
  • MINOR: New features or fields that do not change existing outputs for the same inputs.
  • PATCH: Bug fixes, copy edits, or accessibility changes that do not change intended outputs except for previously incorrect cases.

Review protocol

  • Verify formulas and unit definitions against primary standards or datasets.
  • Run golden-case regression suite and edge-case suite.
  • Record reviewer sign-off with credentials and scope.
  • Document assumptions, limitations, and jurisdiction applicability.

Assumptions & limitations

  • Uses exact unit definitions from the Fidamen conversion library.
  • Internal calculations use double precision; display rounding follows the unit's configured decimal places.
  • Not a substitute for calibrated instruments in regulated contexts.
  • Jurisdiction-specific rules may require official guidance.

Change log

v1.0.0 • 2025-11-22 • MINOR

Initial publication and governance baseline.

Why: Published with reviewed formulas, unit definitions, and UX controls.

Areas: engine, content, ui • Reviewer: Fidamen Standards Committee • Entry ID: 83a80908f45f