Viscosity Converter — cP, mPa·s, cSt and Density

Dynamic viscosity μ (also called absolute viscosity) is measured in Pa·s. Kinematic viscosity ν is measured in m²/s. They are different physical quantities. Convert within five dynamic units (Pa·s, mPa·s, P, cP and kgf·s/m²) or four kinematic units (m²/s, mm²/s, St and cSt) without density. To convert between the groups, choose Calculate with density. No account is required; calculations run in your browser.

1 cP = 1 mPa·s, 1 P = 0.1 Pa·s and 1 kgf·s/m² = 9.80665 Pa·s. For kinematic viscosity, 1 cSt = 1 mm²/s and 1 St = 0.0001 m²/s. The two reference tables keep dynamic and kinematic values separate: corresponding rows do not necessarily describe the same fluid.

Kinematic viscosity is ν = μ / ρ; dynamic viscosity is μ = ν × ρ. These equations use consistent SI units: Pa·s, m²/s and kg/m³. For 20 cP and 800 kg/m³, ν = 0.02 / 800 = 0.000025 m²/s = 25 cSt. Reversing with the same density gives 20 cP.

Density can be entered in kg/m³, g/cm³ or kg/L: 1 g/cm³ = 1 kg/L = 1,000 kg/m³. Nonzero values in cP and cSt have the same number only at a density of 1 g/cm³. Zero remains zero at any positive density. Use density at matching temperature, pressure and other measurement conditions. Dimensionless specific gravity cannot be entered directly: its reference density is also needed.

Enter a nonnegative number using ASCII characters, up to 100 characters. Density must be strictly positive. Decimals and scientific notation such as 1e2 are supported; surrounding whitespace is ignored. Do not include thousands separators, full-width digits or units. Clear inputs removes the active mode’s values while keeping unit selections.

Changing or swapping units retains the input number and interprets it in the new unit. Changing the unit-conversion group resets its unit selections but keeps the value. Density calculations keep separate drafts for each direction. Switching direction alone is not a conversion. Reverse using this result overwrites the other direction’s inputs with the current calculated result and density.

Inputs use double-precision numbers. Results are approximate and displayed with up to 12 significant digits; small and large values use scientific notation. Unrepresentable results are marked Out of range while other valid rows remain available. Precision decreases near the smallest representable values. Displayed digits do not guarantee measurement accuracy. Remove grouping commas before re-entering a displayed result.

Copy includes the selected result, input and, where applicable, density and formula. CSV includes every output-group result, with blank numeric cells and an explicit status for out-of-range rows. Copy, CSV and reverse calculation use values before display rounding. CSV uses UTF-8 with a BOM. Record temperature and other measurement conditions separately. If copying fails, a manual copy field is available; while the browser’s copy request is still pending, wait for it to finish before copying manually because a late write can overwrite the clipboard.

Unit conversion does not correct measurements taken at different temperatures, pressures or shear conditions. Check the original measurement conditions before comparing values. This tool does not model non-Newtonian behaviour, apply temperature corrections, select oil grades or equipment, or estimate viscosity from efflux time in seconds.