Convert kinematic viscosity units — m²/s, Stokes, centistokes, ft²/s and more.
| Unit | Name | Value |
|---|---|---|
| m²/s | Square Meter/Second | 0.00064516 |
| cm²/s | Square Centimeter/Second | 6.4516 |
| St | Stokes | 6.4516 |
| cSt | Centistokes | 645.16 |
| ft²/s | Square Foot/Second | 0.0069444474 |
Formula: Centistokes = in²/s × 645.2
Multiply any in²/s value by 645.2 to get Centistokes.
Reverse: in²/s = Centistokes × 0.00155
Water reference (20°C): 0.001556 in²/s = 1.004 cSt
Values at ~20°C unless noted. Factor: 1 in²/s = 645.2 cSt
| in²/s (in²/s) | Centistokes (cSt) | Fluid |
|---|---|---|
| 2.325e-05 in²/s | 0.015 cSt | Air (20°C) |
| 0.000775 in²/s | 0.5 cSt | Petrol (gasoline) |
| 0.001556 in²/s | 1.004 cSt | Water (20°C) |
| 0.002325 in²/s | 1.5 cSt | Ethanol |
| 0.00465 in²/s | 3 cSt | Diesel fuel |
| 0.05425 in²/s | 35 cSt | SAE 10W motor oil |
| 0.1302 in²/s | 84 cSt | Olive oil |
| 0.155 in²/s | 100 cSt | SAE 30 motor oil |
| 0.279 in²/s | 180 cSt | SAE 90 gear oil |
| 2.186 in²/s | 1410 cSt | Glycerin (20°C) |
| 7.75 in²/s | 5000 cSt | Honey |
| 12.4 in²/s | 8000 cSt | Molasses |
| 77.5 in²/s | 5e+04 cSt | Tomato ketchup |
| 387.5 in²/s | 2.5e+05 cSt | Peanut butter |
| 1.550e+18 in²/s | 1.000e+21 cSt | Glass (room temp) |
1 in²/s = 645.2 cSt.
Water at 20°C = 1 cSt = 0.01 St = 10⁻⁶ m²/s. Use as reference.
Multiply result by 0.00155 to recover the original in²/s value.
Specifies lubricant viscosity grades in cSt at 40°C and 100°C per ISO VG and SAE standards.
Uses kinematic viscosity in cSt for pipeline flow calculations, pump sizing, and heat exchanger design.
Measures crude oil and refined product viscosity in cSt for pipeline transport and refinery design.
Selects hydraulic fluids based on kinematic viscosity in cSt for pump compatibility and system efficiency.
Characterizes food product viscosity (honey, sauces, oils) in cSt for process design and quality control.
Uses ft²/s or cSt for atmospheric kinematic viscosity in Reynolds number calculations for aircraft design.
Square inch per second (in²/s) is occasionally used in US precision engineering and hydraulic system specifications where inch-based units are standard. One in²/s = 6.4516×10⁻⁴ m²/s = 6.4516 St.
In²/s appears in some US hydraulic fluid specifications and industrial machinery manuals. A typical hydraulic fluid at 40°C might be specified as 0.04 in²/s (40 cSt). It is rarely used in modern practice compared to cSt.
Interesting fact: Hydraulic systems in US aircraft were historically specified using in²/s for fluid viscosity, alongside psi for pressure and gpm for flow — a fully inch-pound unit system that required separate conversion when integrating with metric components.
The centistokes (cSt) equals 0.01 Stokes = 10⁻⁶ m²/s and is the most widely used unit for specifying lubricant and fuel viscosity in industry. Water at 20°C has a kinematic viscosity of almost exactly 1 cSt — making it the universal reference.
cSt is the standard unit in lubricant specifications worldwide: ISO viscosity grades (ISO VG 32, 46, 68, 100, etc.) are defined at 40°C in cSt; SAE engine oil grades correlate to cSt at 100°C; ASTM fuel standards specify viscosity in cSt. Virtually every technical datasheet for oils, lubricants, and fuels uses cSt.
Interesting fact: Water's kinematic viscosity of ~1 cSt at 20°C is the reason the centistokes became so practically useful — the reference value is 1, making quick mental comparisons straightforward. Motor oils are typically 30–100 cSt at 40°C; glycerin is about 1,400 cSt; liquid honey 2,000–10,000 cSt.
Kinematic viscosity (ν = μ/ρ) measures how a fluid flows under gravity. The cSt is dominant in industry; m²/s is the SI unit; St and cm²/s are the CGS equivalents. Key anchor: water at 20°C ≈ 1 cSt = 10⁻⁶ m²/s = 0.01 St.
Exact factor: 1 in²/s = 645.2 cSt. Reverse: 1 cSt = 0.00155 in²/s.
All conversions use IEEE 754 double-precision arithmetic, accurate to at least 8 significant figures.