Engineering Units Converter

Why engineering property units must be separated

Engineering handbooks and process notes often mix fluid properties, flow rates, fluxes, porous-media properties, surface-interface values, thermodynamic properties, and rotating machinery data. A direct unit conversion should stay inside one physical quantity. A dynamic viscosity value in cP is not a kinematic viscosity value in cSt unless density is supplied. A mass flow rate in kg/s is not a volume flow rate in L/min unless density is supplied. A molar flow rate cannot become a mass flow rate without molar mass.

The calculator therefore starts with a property-family choice. It converts dynamic viscosity, kinematic viscosity, mass flow rate, volume flow rate, molar flow rate, mass flux density, permeability, surface tension, specific volume, and moment of inertia in separate panels. It does not infer density, molar mass, active area, pore-fluid assumptions, temperature, pressure, geometry, or rigid-body shape factors unless those inputs belong to the same unit family.

Viscosity conversions: Pa*s, cP, St, and cSt

Dynamic viscosity measures resistance to shear and is commonly reported in Pa*s, mPa*s, cP, P, kg/(m*s), lbm/(ft*s), lbm/(ft*h), or slug/(ft*s). The dynamic viscosity panel keeps pound-mass notation explicit so users do not accidentally treat mass-based and force-based viscosity units as the same thing.

Kinematic viscosity is dynamic viscosity divided by density. It is reported as area per time, commonly m2/s, mm2/s, St, cSt, ft2/s, or in2/s. The kinematic viscosity panel handles those units directly, and the optional density bridge relates cP and cSt only when a density value is supplied.

Using the optional cP to cSt density bridge

Some oil, water, and process-fluid references ask for a quick cP to cSt converter or cSt to cP converter. That is not a pure unit conversion, because density has to connect dynamic viscosity and kinematic viscosity. The bridge on this page therefore asks for density in kg/m3 and leaves the main dynamic-viscosity and kinematic-viscosity panels separated.

With density entered, the relationship is straightforward: cSt equals cP divided by density in g/cm3, and cP equals cSt multiplied by density in g/cm3. A density of 1000 kg/m3 is 1 g/cm3, so 1 cP corresponds to 1 cSt only for a fluid close to that density.

Flow rate conversions: mass, volume, and molar throughput

Mass flow rate states how much mass passes a boundary per unit time. Use the mass flow panel for kg/s, kg/min, kg/h, g/s, t/h, lb/s, lb/h, and short ton/h values from process sheets, material balances, or feed-rate notes.

Volume flow rate states how much volume passes per unit time. Use the volume flow panel for m3/s, m3/h, L/s, L/min, L/h, mL/s, US gpm, imperial gpm, ft3/s, ft3/min, and barrels per day. US and UK gallons remain separate because the unit names are easy to confuse.

Molar flow rate states amount of substance per unit time. Use the molar flow panel for mol/s, mol/min, mol/h, mol/day, kmol/s, kmol/min, kmol/h, kmol/day, mmol/s, mmol/min, mmol/h, and lb-mol forms.

Flux, permeability, and surface tension conversions

Mass flux density is mass flow divided by area. Units such as kg/(m2*s), kg/(m2*h), g/(cm2*s), g/(m2*s), lb/(ft2*s), lb/(ft2*h), and kg/(ft2*h) belong together because they are all mass-throughput-per-area values.

Intrinsic permeability is a porous-media property. This suite keeps m2, mm2, um2, nm2, darcy, millidarcy, microdarcy, nanodarcy, cm2, in2, and ft2 in a permeability panel that is explicitly limited to porous-media intrinsic permeability, not hydraulic conductivity, gas-permeability test frameworks, or magnetic permeability.

Surface tension and interfacial tension are force per length. The surface tension panel converts N/m, mN/m, uN/m, dyn/cm, gf/cm, lbf/ft, and lbf/in without mixing them with viscosity or permeability.

Specific volume and moment of inertia conversions

Specific volume is volume per unit mass and is often used in thermodynamics, gas tables, and steam property work. The specific volume panel handles m3/kg, L/kg, cm3/g, mL/g, ft3/lb, in3/lb, and gal/lb. It is related to density by reciprocal logic, but it is not ordinary volume unless mass is known.

Moment of inertia in this page means mass moment of inertia for rotational mechanics. It converts kg*m2, g*cm2, lb*ft2, lb*in2, slug*ft2, and oz*in2. It does not convert area moment of inertia, which belongs to beam and section-property work.

What this consolidation keeps and what stays separate

The old specialist pages overlapped because they all handled fluid or mechanical property unit translation. Combining them into one engineering units converter makes the physical boundaries clearer while keeping each long-tail query represented in panel names, examples, formulas, FAQ coverage, result labels, and redirect anchors.

Pressure, force, torque, power, density, temperature, thermal-property, and electrical converters remain separate pages. They answer broader workflows or different physical quantities and should not be folded into this suite without a future pass that keeps their equations and search intent isolated.