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SimuPipe

Engineering Unit Converter

Convert between common piping and process engineering units. Select a category, enter a value, and see all conversions instantly.

Convert Pressure
All Conversions
Pa
1
kPa
0.001
MPa
0.00000100000
bar
0.0000100000
mbar
0.01
psi
0.000145038
atm
0.00000986923
mmHg
0.00750064
inH₂O
0.00401474
inHg
0.0002953
kg/cm²
0.0000101972
Common Piping Engineering Unit Conversions

Pipe design requires working across unit systems daily. Specifications may arrive in metric (bar, m/s, kg/m3) while vendor datasheets use imperial (psi, ft/s, lb/ft3). A missed conversion in pressure drop, flow rate, or pipe diameter can cascade into incorrect sizing, over-spec'd pumps, or unsafe operating conditions.

This converter covers the units most frequently encountered in hydraulic design: pressure (including lesser-used units like inH2O and mmHg for instrument engineers), volumetric flow rate, dynamic and kinematic viscosity for fluid characterisation, and density for compressible-flow calculations.

Unit Systems

SI (International System): The global standard for engineering. Base units include metres (m), kilograms (kg), seconds (s), and Kelvin (K). Pressure in Pascals (Pa), flow in m3/s, viscosity in Pa-s.

Imperial / US Customary: Still dominant in North American industry. Pressure in psi, flow in GPM, pipe sizes in inches, temperature in Fahrenheit. ASME and API standards primarily use these units.

SimuPipe stores all values internally in SI and converts at the user interface, so you can work in whichever system you prefer without losing precision.

Frequently Asked Questions

What is the difference between dynamic and kinematic viscosity?
Dynamic (absolute) viscosity measures a fluid's internal resistance to flow and has units of Pa.s or cP. Kinematic viscosity is dynamic viscosity divided by density, with units of m2/s or cSt. Kinematic viscosity is what you measure directly with a capillary viscometer. To convert: kinematic viscosity = dynamic viscosity / density.
How do I convert between gauge and absolute pressure?
Absolute pressure = gauge pressure + atmospheric pressure. At sea level, atmospheric pressure is 101.325 kPa (14.696 psi, 1.01325 bar). So 5 bar(g) = 6.01325 bar(a). Vacuum is expressed as negative gauge pressure. This converter handles both gauge and absolute units for pressure.
What is the difference between SCFM and Nm3/h for gas flow?
Both are standardised volumetric flow rates, but at different reference conditions. SCFM (Standard Cubic Feet per Minute) uses 60 degrees F (15.6 degrees C) and 14.696 psia. Nm3/h (Normal Cubic Metres per Hour) uses 0 degrees C and 101.325 kPa. Because the reference temperatures differ, 1 SCFM is approximately 1.583 Nm3/h. Always check which standard your instruments and specifications use.
Why are there so many pressure units in engineering?
Different industries and regions adopted different units historically. Process engineering commonly uses bar or kPa, HVAC uses inches of water or Pa, US oil and gas uses psi, and vacuum systems use Torr or mbar. While SI units (Pa) are the international standard, legacy equipment, codes, and regional practices mean engineers regularly encounter and convert between multiple pressure units.
How do I convert flow rate between volumetric and mass flow?
Mass flow = volumetric flow x density. For example, 10 m3/h of water (density 998 kg/m3) is 9,980 kg/h. For gases, you must specify whether the volumetric flow is at actual (line) conditions or standard conditions, since gas density changes significantly with temperature and pressure. This converter handles volumetric flow units; multiply by your fluid's density to get mass flow.

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