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

1 St = 100 mm2/smm2/s → St
Formula
1 St = 100 mm2/s

Understanding stokes to square millimetres per second Conversion

The stokes (St) is the CGS unit of kinematic viscosity, equal to one square centimetre per second, and the square millimetre per second (mm2/s) is a metric sub-unit that is numerically identical to the widely used centistokes. Because a centimetre is 10 millimetres, one stokes contains 100 mm2/s. This conversion is especially handy in lubricant and fuel testing, where instruments report centistokes but data sheets sometimes list mm2/s.

Conversion Formula

1 St=100 mm2/s1\ \text{St} = 100\ \text{mm2/s}

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

mm2/s=St×100\text{mm2/s} = \text{St} \times 100

Step-by-Step Example

Convert 25 stokes to square millimetres per second.

mm2/s=25×100=2500 mm2/s\text{mm2/s} = 25 \times 100 = 2500\ \text{mm2/s}

How to Convert stokes to square millimetres per second

Turning stokes into square millimetres per second (centistokes) is a simple multiply-by-100 operation.

  1. Take the stokes reading: Start with the kinematic viscosity in St.
  2. Multiply by 100: Each stokes holds 100 mm2/s.
  3. Interpret the result: The value in mm2/s is the same as the centistokes figure used on most oil data sheets.
  4. Worked result: 25 St × 100 = 2500 mm2/s.

stokes to square millimetres per second conversion table

stokes (St)square millimetres per second (mm2/s)
00
1100
2200
3300
4400
5500
6600
7700
8800
9900
101000
151500
202000
252500
303000
404000
505000
606000
707000
808000
909000
10010000
15015000
20020000
25025000
30030000
40040000
50050000
60060000
70070000
80080000
90090000
1000100000
2000200000
3000300000
4000400000
5000500000
100001000000
250002500000
500005000000
10000010000000
25000025000000
50000050000000
1000000100000000

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}.

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}.

Frequently Asked Questions

How many square millimetres per second are in one stokes?

One stokes equals 100 mm2/s. This factor of 100 arises because a centimetre contains ten millimetres, and the length ratio is squared for area.

Is a square millimetre per second the same as a centistokes?

Yes. One mm2/s is numerically identical to one centistokes, which is why lubricant grades are often quoted in either unit interchangeably.

How do I convert square millimetres per second back to stokes?

Multiply the mm2/s value by 0.01. For example, 100 mm2/s equals 1 St.

Why is this conversion common in oil analysis?

Viscometers report kinematic viscosity in centistokes (mm2/s), and engine or turbine oil specifications frequently use the same unit, so converting from stokes keeps the numbers consistent.

What is water's viscosity in these units?

Water near 20 °C is roughly 1 mm2/s, equal to about 0.01 St.

People also convert

St to m2/sSt to cStSt to ft2/s

Complete stokes conversion table

St
UnitResult
square metres per second (m2/s)0.0001 m2/s
square millimetres per second (mm2/s)100 mm2/s
centistokes (cSt)100 cSt
square feet per second (ft2/s)0.001076391 ft2/s

Kinematic viscosity conversions