Centistokes to Stokes Kinematic Viscosity Converter
Common Conversions
| cSt | St |
|---|---|
| 0.1 | 0.001 |
| 0.5 | 0.005 |
| 1 | 0.01 |
| 2 | 0.02 |
| 5 | 0.05 |
| 10 | 0.1 |
| 25 | 0.25 |
| 50 | 0.5 |
| 100 | 1 |
| 1000 | 10 |
Why this conversion matters in chemistry
ISO lubricant grading runs in centistokes at 40 °C — an ISO VG 46 oil sits at 41.4–50.6 cSt. Older CGS fluid-mechanics references and petroleum handbooks use stokes. An ISO VG 100 oil at 100 cSt lands at exactly 1 St — the same kinematic viscosity in CGS units of cm²/s. A factor of 0.01 St per cSt comes from the centi prefix. The conversion sits at the handoff between modern lubricant specifications and the legacy literature where viscosity sits in stokes rather than the cSt or mm²/s a contemporary capillary viscometer reports.
Formula
St = cSt ÷ 100
Worked Examples
1 cSt = 0.01 St
Water at 20 °C — the calibration anchor at the low-viscosity end.
100 cSt = 1 St
An ISO VG 100 lubricant — the bridge anchor in CGS units.
32 cSt = 0.32 St
A typical hydraulic-fluid viscosity at 40 °C in CGS units.
Frequently Asked Questions
How do I convert centistokes to stokes?
Divide by 100. The centi prefix is 1/100 by definition, so 1 cSt = 0.01 St. Equivalently, 1 cSt = 1 mm²/s in SI form.
What is kinematic viscosity?
Kinematic viscosity ν = η/ρ — dynamic viscosity divided by density. It captures how fast a fluid flows under gravity, in units of cm²/s (stokes) or mm²/s (centistokes). Capillary viscometers measure ν directly off a timed flow through a calibrated bore.
Why does petroleum spec in kinematic viscosity?
ASTM standards for engine oils, fuels, and lubricants are written around kinematic viscosity because the standard glass-capillary viscometer measures ν directly, with no need to weigh the sample for density. The convention sticks because the measurement is what the spec is designed around.