Knowledge / Fundamentals
Pascal is the SI unit for pressure. In differential pressure measurement, you also encounter millibar, millimetre water column and inch water column. This page explains each unit, shows a full conversion table and provides an interactive calculator.
A
Enter a value — all other units are calculated instantly.
B
| Pa | hPa / mbar | mmH₂O | inWC | mmHg |
|---|---|---|---|---|
| 1 | 0.01 | 0.10197 | 0.00401 | 0.0075 |
| 10 | 0.1 | 1.0197 | 0.04015 | 0.07501 |
| 50 | 0.5 | 5.0986 | 0.20073 | 0.37503 |
| 100 | 1 | 10.1972 | 0.40146 | 0.75006 |
| 200 | 2 | 20.3943 | 0.80293 | 1.5001 |
| 500 | 5 | 50.9858 | 2.0073 | 3.7503 |
| 1000 | 10 | 101.972 | 4.0146 | 7.5006 |
| 1800 | 18 | 183.549 | 7.2263 | 13.5011 |
C
The SI base unit for pressure, defined as 1 newton per square metre (N/m²). In the low-pressure range below 2,000 Pa — typical for cleanroom cascades, filter monitoring and biogas — Pascal is the most common unit. Our ring-balance gauges measure from 40 Pa to 1,800 Pa.
100 Pa. Well known from meteorology (atmospheric pressure ~1,013 hPa). Less common in industrial measurement, but occasionally encountered in HVAC applications at the higher end of differential pressure ranges.
Identical to hPa: 1 mbar = 1 hPa = 100 Pa. Was the standard pressure unit in meteorology and engineering before SI adoption. Still widely used in gas measurement and flow applications.
Simply put: in a U-tube manometer, the water level on one side would rise by exactly 1 mm. 1 mmH₂O = 9.80665 Pa. Historically the most common unit for small differential pressures in HVAC and chimney draught. Many older systems and standards still use mmH₂O — conversion to Pa: value × 9.807.
Widely used in North America: 1 inWC = 249.089 Pa ≈ 25.4 mmH₂O. Standard in US HVAC codes and fan specifications. Often the interface point between European (Pa/mmH₂O) and US (inWC) dimensioning on international projects.
1 mmHg = 133.322 Pa. Classic in medicine (blood pressure) and vacuum technology. Rarely used in differential pressure measurement for gases, but may appear as a reference value in laboratory and pharmaceutical applications.
D
Pascal values can seem abstract. These comparisons show what the numbers actually feel like.
A standard A4 sheet (80 g/m²) lying flat on a desk exerts roughly 0.8 Pa on the surface beneath it.
The gentle air movement when a person walks directly past you creates roughly 10 Pa of dynamic pressure.
A lightweight paperback (~300 g) resting on an A4 sheet of paper presses down with approximately 47 Pa.
A 1-cent euro coin (2.3 g, 16 mm diameter) lying flat on a surface exerts about 109 Pa on its footprint.
Breathing through an FFP2 mask creates a resistance of roughly 200–300 Pa — that slight effort you feel with every breath.
When your head is just 10 cm below the pool surface, water pressure on your eardrums is about 980 Pa — noticeable but not painful.
Your application
Our mechanical ring-balance gauges measure differential pressure in the low-pressure range without drift, without recalibration, ATEX-certified and Made in Germany.