square millimetres per second (mm2/s) to stokes (St) conversion

1 mm2/s = 0.01 StSt → mm2/s
Formula
1 mm2/s = 0.01 St

Understanding Square Millimetres Per Second to Stokes Conversion

The square millimetre per second (mm²/s) is a metric unit of kinematic viscosity equal to the centistokes, while the stokes (St) is the base CGS unit equal to one square centimetre per second. Because a square centimetre holds one hundred square millimetres, one mm²/s equals a hundredth of a stokes. This conversion links everyday lubricant viscosities with the whole-stokes figures found in older CGS rheology data.

Conversion Formula

1 mm2/s=0.0100000 St1\ \text{mm2/s} = 0.0100000\ \text{St}

To convert square millimetres per second to stokes, multiply by this factor:

St=mm2/s×0.01\text{St} = \text{mm2/s} \times 0.01

Step-by-Step Example

Convert 25 square millimetres per second to stokes.

St=25×0.01=0.25 St\text{St} = 25 \times 0.01 = 0.25\ \text{St}

How to Convert Square Millimetres Per Second to Stokes

Use this method to express a metric viscosity value in CGS stokes.

  1. Note the factor: One square millimetre per second equals 0.01 stokes.
  2. Take your value: Record the kinematic viscosity in mm²/s (equivalently centistokes).
  3. Multiply: Multiply by 0.01 to obtain stokes.
  4. Worked result: For 25 mm²/s, 25 × 0.01 = 0.25 St.

square millimetres per second to stokes conversion table

square millimetres per second (mm2/s)stokes (St)
00
10.01
20.02
30.03
40.04
50.05
60.06
70.07
80.08
90.09
100.1
150.15
200.2
250.25
300.3
400.4
500.5
600.6
700.7
800.8
900.9
1001
1501.5
2002
2502.5
3003
4004
5005
6006
7007
8008
9009
100010
200020
300030
400040
500050
10000100
25000250
50000500
1000001000
2500002500
5000005000
100000010000

What is the square millimetre per second?

The square millimetre per second (mm²/s) is the practical SI unit of kinematic viscosity, numerically identical to the centistokes (cSt). It is the unit in which most liquid viscosities are quoted in engineering and lubrication data sheets.

Definition

One square millimetre per second is one millionth of a square metre per second:

1 mm2/s=0.000001 m2/s1\ \text{mm}^2/\text{s} = 0.000001\ \text{m}^2/\text{s}

Because 1 mm=10−3 m1\ \text{mm} = 10⁻³\ \text{m}, area scales as 10−610⁻⁶, so 1 mm2/s=10−6 m2/s1\ \text{mm}^2/\text{s} = 10⁻⁶\ \text{m}^2/\text{s}. It is exactly equal to one centistokes: 1 mm2/s=1 cSt1\ \text{mm}^2/\text{s} = 1\ \text{cSt}.

Origin and History

As the SI displaced the CGS system, the centistokes was re-expressed in coherent SI form as mm²/s, keeping the numerical values in existing tables unchanged. This convenient one-to-one equality made the transition seamless for industries such as petroleum and lubricants that had decades of data in centistokes.

Law and Notable Facts

It is a coherent submultiple within SI usage and the de facto standard for viscosity grades. ISO viscosity grade (VG) numbers, such as ISO VG 46, are defined by the fluid's mid-point kinematic viscosity in mm²/s at 40 °C — so ISO VG 46 oil is nominally 46 mm²/s at 40 °C.

Real-World Examples and Conversions

Water at 20 °C is about 1.004 mm²/s (1.004 cSt). Typical engine oil at 100 °C ranges from roughly 5 to 21 mm²/s depending on SAE grade. One mm2/s\text{mm}^2/\text{s} equals 10−6 m2/s10⁻⁶\ \text{m}^2/\text{s} and 10−2 stokes10⁻²\ \text{stokes}.

What is the stokes?

The stokes (St) is the CGS unit of kinematic viscosity, equal to one square centimetre per second. Its common submultiple, the centistokes (cSt), is the everyday unit for reporting the kinematic viscosity of oils and other liquids.

Definition

One stokes equals one square centimetre per second, which in SI units is:

1 St=0.0001 m2/s1\ \text{St} = 0.0001\ \text{m}^2/\text{s}

Because 1 cm=10−2 m1\ \text{cm} = 10⁻²\ \text{m}, area scales as 10−410⁻⁴, so 1 St=1 cm2/s=10−4 m2/s1\ \text{St} = 1\ \text{cm}^2/\text{s} = 10⁻⁴\ \text{m}^2/\text{s} exactly. One hundredth of a stokes is a centistokes: 1 cSt=10−6 m2/s=1 mm2/s1\ \text{cSt} = 10⁻⁶\ \text{m}^2/\text{s} = 1\ \text{mm}^2/\text{s}.

Origin and History

The unit is named after the Irish-British mathematician and physicist Sir George Gabriel Stokes (1819–1903), whose work on fluid dynamics includes Stokes' law for the drag on a sphere and the Navier–Stokes equations. It was introduced as the natural CGS unit for kinematic viscosity, paralleling the poise for dynamic viscosity.

Law and Notable Facts

The stokes is a CGS unit and is not part of SI, which uses m²/s. Kinematic viscosity in stokes equals dynamic viscosity in poise divided by density in g/cm³ — a clean relationship within the CGS system, since water's density is very close to 1 g/cm³.

Real-World Examples and Conversions

Water at 20 °C has a kinematic viscosity of about 0.01 St, i.e. roughly 1 cSt. One stokes (10−4 m2/s10⁻⁴\ \text{m}^2/\text{s}, or 100 cSt) is comparable to a moderately heavy oil. To convert, 1 St=100 cSt=100 mm2/s1\ \text{St} = 100\ \text{cSt} = 100\ \text{mm}^2/\text{s}, and 1 m2/s=10,000 St1\ \text{m}^2/\text{s} = 10{,}000\ \text{St}.

Frequently Asked Questions

How many stokes are in one square millimetre per second?

One square millimetre per second equals 0.01 stokes, because a stokes is one square centimetre per second and a square centimetre holds 100 square millimetres.

What is the conversion formula?

Multiply the mm²/s value by 0.01. For example, 46 mm²/s equals 0.46 St.

How does this relate to centistokes?

Since 1 mm²/s equals 1 centistokes and 1 stokes equals 100 centistokes, dividing by 100 (multiplying by 0.01) converts mm²/s directly to stokes.

When is expressing viscosity in stokes useful?

Whole-stokes figures appear in classical fluid-mechanics texts and older CGS datasets, so converting practical mm²/s values into stokes aids comparison with that literature.

How do I convert stokes back to mm²/s?

Multiply the stokes value by 100, so 0.25 St equals 25 mm²/s.

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Complete square millimetres per second conversion table

mm2/s
UnitResult
square metres per second (m2/s)0.000001 m2/s
stokes (St)0.01 St
centistokes (cSt)1 cSt
square feet per second (ft2/s)0.00001076391 ft2/s

Kinematic viscosity conversions