What is the viscosity of water?

1.002 mPa·s at 20 °C, which is close enough to 1 that the millipascal-second and the centipoise are treated as the same unit. Water's viscosity is strongly temperature dependent: 1.792 mPa·s at 0 °C, 1.002 at 20 °C, 0.653 at 40 °C and 0.282 at 100 °C. Below about 0 °C it rises steeply, which is why cold water is noticeably harder to pump.

What is the difference between cSt and cP?

The centistoke (cSt) is kinematic viscosity in mm²/s; the centipoise (cP) is dynamic viscosity in mPa·s. They differ by the fluid's density: cSt = cP ÷ (density in g/cm³). For water, whose density is about 1 g/cm³, the two numbers coincide — which is why they are so often confused. For mercury, at 13.5 g/cm³, a 1.55 cP dynamic viscosity corresponds to only 0.115 cSt.

What does the ISO VG number mean?

It is the kinematic viscosity in cSt at 40 °C, by definition — an ISO VG 46 oil measures 46 cSt at 40 °C, an ISO VG 32 measures 32. The grades follow a standard preferred-number series with ±10% tolerance. The number says nothing about how the oil behaves at other temperatures, which is what the viscosity index describes.

Why do gases get more viscous when heated?

Because gas viscosity comes from momentum transfer between molecules rather than from intermolecular attraction. Heating makes the molecules move faster, so they transfer momentum more effectively across a shear layer, and viscosity rises. Air goes from 0.0182 mPa·s at 20 °C to 0.0218 at 100 °C. Liquids behave the opposite way, because heating weakens the intermolecular bonds that resist sliding.

Do I use dynamic or kinematic viscosity for pressure drop?

Dynamic viscosity, in the Reynolds number and in the Darcy-Weisbach friction factor. Kinematic viscosity appears in gravity-driven and open-channel work, and in the pipe-sizing nomograms some handbooks publish. If a formula asks for viscosity without specifying, check its units: Pa·s or cP means dynamic, m²/s or cSt means kinematic. Using the wrong one is a common source of large errors.

Viscosity Chart

Dynamic and kinematic viscosity for 26 common fluids at 0 °C to 100 °C, with density — so you can move between the two viscosity measures without a second table.

Data verified 2026-09-29 · based on ISO 3448:1992

Quick Answer

Water at 20 °C is 1.002 mPa·s, which is why the millipascal-second is also called the centipoise. Glycerol at 1 412 mPa·s is about 1 400 times water and honey about 10 000 times. Liquids get thinner as they heat; gases get thicker — the opposite behaviour, and the reason hot air is harder to push through a duct than cold.

Find a fluid

Viscosity of Common Fluids

Fluid^[2]	Temperature °C^[2]	Dynamic viscosity mPa·s^[2]	Kinematic viscosity mm²/s (cSt)^[1]	Density kg/m³^[2]	Note^[2]
Water (0 °C) #	0	1.792	1.792	1000	Water thickens markedly as it cools
Water (10 °C) #	10	1.307	1.307	1000
Water (20 °C) #	20	1.002	1.004	998	The reference point where water's viscosity is about 1 mPa·s
Water (40 °C) #	40	0.653	0.6583	992
Water (60 °C) #	60	0.467	0.4751	983
Water (80 °C) #	80	0.355	0.3652	972
Water (100 °C) #	100	0.282	0.2944	958	At boiling point — viscosity has fallen by a factor of 6.4
Sea water (3.5%, 20 °C) #	20	1.07	1.044	1025	Slightly more viscous than fresh water
Ethanol (20 °C) #	20	1.1	1.394	789	Similar to water despite much lower density
Methanol (20 °C) #	20	0.59	0.7449	792	Less viscous than ethanol
Ethylene glycol (20 °C) #	20	16.1	14.47	1113	16 times water — a real pumping cost in antifreeze loops
Glycerol (20 °C) #	20	1412	1120	1261	Extremely viscous; about 1 400 times water
Mercury (20 °C) #	20	1.55	0.1145	13534	Low viscosity despite very high density — hence a low kinematic value
Kerosene (20 °C) #	20	1.64	2.025	810
Gasoline (20 °C) #	20	0.6	0.8108	740	Low viscosity, low flash point
Diesel fuel (20 °C) #	20	3	3.529	850	Varies with grade; winter diesel is thinner
Hydraulic oil ISO VG 46 (40 °C) #	40	40.3	46	876	The ISO VG grade number is 46 cSt at 40 °C by definition — the dynamic value is that times density
Hydraulic oil ISO VG 46 (100 °C) #	100	5.71	6.798	840	A viscosity index of about 100, which is the conventional hydraulic oil target
Engine oil SAE 30 (40 °C) #	40	88	100	880	Monograde reference; the grade is set kinematically
Engine oil SAE 15W-40 (40 °C) #	40	91.9	105	875	The W number rates cold behaviour, the second number hot
Engine oil SAE 15W-40 (100 °C) #	100	12.2	14.52	840	From a published kinematic value of 14.5 cSt at 100 °C
Honey (20 °C) #	20	1e+04	7042	1420	Roughly 10 000 times water in dynamic viscosity
Air (20 °C) #	20	0.0182	15.1	1.205	Gases are two to five orders of magnitude less viscous than liquids
Air (100 °C) #	100	0.0218	23.04	0.946	Gas viscosity rises with temperature — the opposite of liquids
Carbon dioxide (20 °C) #	20	0.0147	7.436	1.977
Steam, saturated (100 °C) #	100	0.0123	20.57	0.598

Dynamic viscosity (mPa·s, also called the centipoise) is the fluid's internal resistance to shear. Kinematic viscosity (mm²/s, also called the centistoke) is the dynamic value divided by density, and is what oil grades are specified in — an ISO VG 46 oil has a kinematic viscosity of 46 cSt at 40 °C by definition. Because the conversion needs density, a fluid with a high density but a low dynamic viscosity, such as mercury, has an unexpectedly low kinematic viscosity. The same fluid appears more than once at different temperatures, because the temperature dependence is larger than the difference between many fluids.

Dynamic vs Kinematic — Which Number You Need

The two viscosity measures answer different questions, and using the wrong one is a common source of a factor-of-a-thousand error.

Dynamic viscosity (µ, mPa·s or cP) is a force-per-area quantity. It is what appears in the Reynolds number, in pressure-drop equations, in bearing and lubrication calculations, and in anything involving shear stress. Its SI unit is the pascal-second, so mPa·s is 0.001 Pa·s — and 1 mPa·s equals 1 centipoise exactly, which is why the older unit survives so completely.

Kinematic viscosity (ν, mm²/s or cSt) is dynamic viscosity divided by density. It is what appears in gravity-driven flow, in pipe-sizing nomograms, and in oil grading. Its SI unit is m²/s, which is far too large for practical fluids, so mm²/s — identical to the centistoke — is the working unit.

The relationship is ν = µ/ρ. Because density is in the denominator, two fluids with the same dynamic viscosity can have very different kinematic viscosities: mercury at 1.55 mPa·s has a kinematic viscosity of only 0.115 cSt, because its density is 13 534 kg/m³. Conversely, ISO VG oil grades are specified kinematically, so an ISO VG 46 oil must measure 46 cSt at 40 °C regardless of its additive package.

Why Temperature Changes Everything

Viscosity is far more temperature-sensitive than almost any other fluid property, and the sensitivity runs in opposite directions for liquids and gases.

Liquids thin as they heat. Water drops from 1.792 mPa·s at 0 °C to 0.282 at 100 °C — a factor of 6.4. Engine oil changes far more: an SAE 15W-40 goes from about 105 mPa·s at 40 °C to 14.5 at 100 °C, and at −20 °C it would be several thousand. This is why multi-grade oils exist and why the viscosity index is a specification in its own right — it describes how flat the viscosity-temperature curve is.

Gases thicken as they heat. Air rises from 0.0182 mPa·s at 20 °C to 0.0218 at 100 °C, an increase of 20%. The mechanism is different: in a liquid, molecules are close together and heating loosens the bonds that resist sliding, while in a gas momentum transfer between molecules increases with their speed. The practical consequence is that hot air is harder to push through a duct than cold air, even though its density is lower — an effect that surprises people sizing exhaust systems.

For any calculation where viscosity appears, use the value at the operating temperature, not at 20 °C. A pressure-drop calculation done with room-temperature viscosity for a fluid at 80 °C can be out by a factor of three or more.

Frequently Asked Questions

What is the viscosity of water?: 1.002 mPa·s at 20 °C, which is close enough to 1 that the millipascal-second and the centipoise are treated as the same unit. Water's viscosity is strongly temperature dependent: 1.792 mPa·s at 0 °C, 1.002 at 20 °C, 0.653 at 40 °C and 0.282 at 100 °C. Below about 0 °C it rises steeply, which is why cold water is noticeably harder to pump.
What is the difference between cSt and cP?: The centistoke (cSt) is kinematic viscosity in mm²/s; the centipoise (cP) is dynamic viscosity in mPa·s. They differ by the fluid's density: cSt = cP ÷ (density in g/cm³). For water, whose density is about 1 g/cm³, the two numbers coincide — which is why they are so often confused. For mercury, at 13.5 g/cm³, a 1.55 cP dynamic viscosity corresponds to only 0.115 cSt.
What does the ISO VG number mean?: It is the kinematic viscosity in cSt at 40 °C, by definition — an ISO VG 46 oil measures 46 cSt at 40 °C, an ISO VG 32 measures 32. The grades follow a standard preferred-number series with ±10% tolerance. The number says nothing about how the oil behaves at other temperatures, which is what the viscosity index describes.
Why do gases get more viscous when heated?: Because gas viscosity comes from momentum transfer between molecules rather than from intermolecular attraction. Heating makes the molecules move faster, so they transfer momentum more effectively across a shear layer, and viscosity rises. Air goes from 0.0182 mPa·s at 20 °C to 0.0218 at 100 °C. Liquids behave the opposite way, because heating weakens the intermolecular bonds that resist sliding.
Do I use dynamic or kinematic viscosity for pressure drop?: Dynamic viscosity, in the Reynolds number and in the Darcy-Weisbach friction factor. Kinematic viscosity appears in gravity-driven and open-channel work, and in the pipe-sizing nomograms some handbooks publish. If a formula asks for viscosity without specifying, check its units: Pa·s or cP means dynamic, m²/s or cSt means kinematic. Using the wrong one is a common source of large errors.

Value Sources

Each data column on this page is tied to the source it came from. The numbers in square brackets correspond to the table headers above.

#	Source	Type	Revision / method
[1]	Kinematic viscosity computed from dynamic viscosity and density	derived	ν (mm²/s) = µ (mPa·s) ÷ ρ (kg/m³) × 1000, which is the standard ν = µ/ρ relationship with the units reconciled. Anchored by known-value checks — water at 20 °C must come out at 1.004 cSt and ISO VG 46 oil at exactly 46 cSt at 40 °C, since that is the definition of the grade.
[2]	Published viscosity data for common fluids	standard	compilations as published 2024–2026

Data Sources

Standard	Revision	What it covers on this page
ISO 3448 — Industrial lubricants, classification of viscosity grades	ISO 3448:1992	the ISO VG grade definitions
ASTM D445 — Kinematic Viscosity of Transparent and Opaque Liquids	ASTM D445-23	the measurement method behind the kinematic values
NIST reference data for water and air viscosity	NIST Standard Reference Database 69 and IAPWS formulations, 2023	the water and air values across temperature

Cross-checked against:

Water viscosity checked against the IAPWS formulation at six temperatures from 0 °C to 100 °C
Air viscosity checked against the NIST reference data at two temperatures, including the direction of the temperature dependence
Oil grades verified against their ISO VG definitions — the grade number must equal the kinematic viscosity at 40 °C
Kinematic values recomputed from dynamic viscosity and density at build time

Derived values — the following values on this page are calculated, not taken directly from the standard:

Value	How it is derived
Kinematic viscosity in mm²/s (cSt)	ν = µ/ρ with µ in mPa·s and ρ in kg/m³, multiplied by 1000 to give mm²/s. Anchored by two known-value checks that would fail if the reference were misapplied: water at 20 °C must be 1.004 cSt and ISO VG 46 oil must be exactly 46 cSt at 40 °C.

Values are typical published figures at the stated temperature. Viscosity is the most temperature-sensitive property in this chart — a factor of two or more over a 40 °C change is normal for oils — so always use the value at the operating temperature. Non-Newtonian fluids such as grease, slurry and many food products have no single viscosity at all; their apparent viscosity depends on shear rate and they are not represented here.

Accuracy and use. The values on this page are compiled from the published standards and cross-checked sources listed above. Where values are derived, the derivation is stated. No warranty, express or implied, is made as to the accuracy or completeness of this information, and no liability is accepted for any loss or damage arising from its use. Engineering reference data is provided for guidance in preliminary work — before a value is used for design, fabrication or acceptance testing, verify it against the current revision of the governing standard and against your own inspection. The user assumes all risk and responsibility in connection with the use of this information.

Cite This Page

Every value on this page is traceable to the sources listed above. If you use the data in a document, paper or report, cite it as:

Plain text

Engineering Reference. "Viscosity Chart." https://refmanual.com/charts/viscosity-chart/ (accessed 2026-09-29). Data from ISO 3448 — Industrial lubricants, classification of viscosity grades, ISO 3448:1992.

BibTeX

@misc{viscosity-chart,
  title        = {Viscosity Chart},
  author       = {{Engineering Reference}},
  howpublished = {\url{https://refmanual.com/charts/viscosity-chart/}},
  note         = {Accessed: 2026-09-29},
  source       = {ISO 3448 — Industrial lubricants, classification of viscosity grades, ISO 3448:1992}
}

RIS (EndNote, Zotero, Mendeley)

TY  - ELEC
TI  - Viscosity Chart
AU  - Engineering Reference
PB  - Engineering Reference
UR  - https://refmanual.com/charts/viscosity-chart/
PY  - 2026
DA  - 2026-09-29
N1  - Source: ISO 3448 — Industrial lubricants, classification of viscosity grades, ISO 3448:1992
ER  -

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