Pressure Unit Converter

Pressure is quoted in bar on a European transmitter, psi on a US one, kPa on a panel label and metres of water on a pump curve — four numbers for one physical quantity. This converter moves between them exactly, including the process-specific units mH₂O and mmHg.

Convert pressure unit units

Value

From

Why so many pressure units

Pressure is force per area, and every industry settled on a different force and area convention. bar and kPa are metric and SI-friendly; psi is the imperial shop standard; mH₂O and mmHg are practical head units that tie pressure to a column of liquid, which is what a pump or a manometer actually shows.

All of these are exact conversions with no assumption about the fluid except mH₂O, which assumes water at about 4 °C. For other liquids the head changes with density, so convert the numeric value but keep the application in mind.

Which unit to specify

For transmitter selection and datasheets, bar, psi and kPa are interchangeable and the choice is regional. mH₂O belongs on pump curves and level calculations; mmHg on vacuum and laboratory manometry. Pick the unit your permit or standard writes in, then convert for internal use.

Complete conversion reference

Convert 1 unit to	Pa	kPa	MPa	bar	mbar	psi	mH₂O	mmHg
1 Pa	1	0.001	1e-06	1e-05	0.01	0.000145038	0.000101972	0.00750062
1 kPa	1000	1	0.001	0.01	10	0.145038	0.101972	7.50062
1 MPa	1e+06	1000	1	10	10000	145.038	101.972	7500.62
1 bar	100000	100	0.1	1	1000	14.5038	10.1972	750.062
1 mbar	100	0.1	0.0001	0.001	1	0.0145038	0.0101972	0.750062
1 psi	6894.76	6.89476	0.00689476	0.0689476	68.9476	1	0.70307	51.7149
1 mH₂O	9806.65	9.80665	0.00980665	0.0980665	98.0665	1.42233	1	73.5559
1 mmHg	133.322	0.133322	0.000133322	0.00133322	1.33322	0.0193368	0.0135951	1

Instruments for this measurement

S3000CG

Gauge pressure transmitter

0–0.6 … 0–60 MPa

S3000CD

Differential pressure transmitter

Orifice / level / flow

S3000CA

Absolute pressure transmitter

Vacuum to high range

S3000H

Sanitary pressure transmitter

CIP / food & pharma

Pressure Transmitter Selection Guide

Process-first, not brand-first

Wet side & range method

Models shown are representative families, not a complete catalogue. Send us your application, water analysis and installation constraints and we will match instruments to it.

Frequently asked

How many psi in a bar?

One bar is 14.5038 psi. Conversely 1 psi is 6.8948 kPa. This converter keeps the full set so you can move between any of them directly.

What is 1 mH₂O in bar?

About 0.0980665 bar, or 9.80665 kPa, assuming water at 4 °C. mH₂O is a head unit, so it describes the pressure a column of water exerts and is common on pump and level data.

Is kPa the same as mbar?

Numerically 1 mbar = 100 Pa = 0.1 kPa, so they differ by a factor of 100. kPa is the SI-preferred unit; mbar is still common on instrument ranges.

When should I use absolute vs gauge pressure?

Gauge (barg, psig) reads relative to atmosphere and is what most process instruments display. Absolute (bara, psia) includes atmospheric pressure and is needed for vacuum, boiling point and gas-law calculations. The converter handles the numeric value; the reference frame is a separate choice.

This page performs exact unit arithmetic with no physical assumption beyond the stated reference (for example mH₂O assumes water near 4 °C, and pH follows its logarithmic definition). It is a working aid, not a substitute for the measurement method named in your permit.