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Convert Pascals to Millimeters of Mercury - Pressure Converter

This converter transforms a pressure value expressed in kilopascals (kPa) into millimeters of mercury (mmHg). The relationship is a fixed mathematical conversion based on internationally accepted definitions of the pascal and the standard atmosphere.

Use this tool for laboratory calculations, clinical readings, HVAC and meteorological conversions. For safety‑critical or regulatory reporting, follow calibrated instrument procedures and maintain traceability to accredited standards.

Updated Nov 11, 2025

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Methodology

The conversion is derived from the relationship between the pascal and the millimeter of mercury under internationally referenced definitions. One standard approach uses the internationally accepted conventional standard atmosphere where 1 atmosphere equals 101325 pascals and 1 atmosphere equals 760 mmHg. From these definitions the conversion factor is determined and applied consistently.

Millimeter of mercury (mmHg) is often treated interchangeably with the torr in many practical contexts, but small differences can arise depending on whether mmHg is defined by a mercury column under local gravity and temperature. For metrological traceability and reporting, follow accredited calibration procedures such as ISO/IEC 17025 and reference material or standards published by national metrology institutes.

When reporting converted values, account for significant figures and environmental dependencies when relevant. For most conversions at common laboratory accuracy needs, the standard factor below is sufficient; for high-precision needs consult primary standards and calibration reports.

Worked examples

Example 1: 101.325 kPa × 7.500616827 ≈ 760.000 mmHg (standard atmospheric pressure).

Example 2: 5 kPa × 7.500616827 ≈ 37.503 mmHg.

Further resources

Expert Q&A

Is mmHg the same as torr?

In many practical applications mmHg and the torr are used interchangeably and differ by less than a few parts in 10 million when both are referenced to the conventional standard atmosphere. For metrology or legal contexts, confirm the exact definition required by the specification because the torr is defined as 1/760 of a standard atmosphere while mmHg can be defined by a physical mercury column under local conditions.

How accurate is this conversion factor?

The factor used here is based on internationally accepted constants and is suitable for general laboratory, clinical and industrial work. For high-precision work, consider the uncertainty of your instruments, environmental effects on mercury density and gravity, and use calibration traceable to an accredited national metrology institute. See ISO/IEC 17025 for laboratory calibration requirements and NIST references for unit definitions.

Do I need to correct for temperature or gravity?

The theoretical conversion uses fixed constants. If the mmHg reading is derived from a physical mercury column or manometer, temperature and local gravity will affect the reading and must be corrected for high-accuracy measurements. Electronic sensors typically report in pascals and internal algorithms may compensate; check the instrument documentation and calibration certificate.

What rounding or significant figures should I use?

Match rounding to the uncertainty of your input measurement or to the reporting rules of your application. For typical sensor readings, two to three decimal places in mmHg are common. For regulatory or scientific reporting, propagate the measurement uncertainty and report appropriate significant figures.

Are there regulatory considerations when converting pressures for workplace or clinical use?

Yes. For workplace safety reporting, exposure limits and instrument calibration procedures may be governed by regulations. Follow applicable agency requirements and ensure instruments are calibrated to standards traceable to national metrology institutes. Consult regulatory guidance for your jurisdiction when conversions are used for compliance.

Sources & citations