🛢️ Oil & Water Viscosity Converter 2026
Convert viscosity units and compare fluids at different temperatures
1 cP = 0.001 Pa·s
Formula: value × 0.001
📊 Common Fluid Viscosities at Selected Temperature
Water Viscosity vs Temperature
| Temperature | Dynamic Viscosity (cP) | Pa·s |
|---|---|---|
| 0°C (32°F) | 1.792 | 0.001792 |
| 20°C (68°F) | 1.002 | 0.001002 |
| 25°C (77°F) | 0.890 | 0.000890 |
| 40°C (104°F) | 0.653 | 0.000653 |
| 60°C (140°F) | 0.467 | 0.000467 |
| 80°C (176°F) | 0.355 | 0.000355 |
| 100°C (212°F) | 0.282 | 0.000282 |
SAE Motor Oil Viscosity Grades
| SAE Grade | Low Temp (-18°C) | High Temp (100°C) | Typical Use |
|---|---|---|---|
| SAE 5W | ≤ 6,600 cP | ≥ 3.8 cSt | Cold weather, fuel economy |
| SAE 10W | ≤ 7,000 cP | ≥ 4.1 cSt | Moderate cold |
| SAE 20W | ≤ 9,500 cP | ≥ 5.6 cSt | Light cold weather |
| SAE 30 | — | 9.3–12.5 cSt | Warm weather |
| SAE 40 | — | 12.5–16.3 cSt | Hot weather, heavy duty |
| SAE 5W-30 | ≤ 6,600 cP | 9.3–12.5 cSt | All-season, common |
| SAE 10W-40 | ≤ 7,000 cP | 12.5–16.3 cSt | All-season, older engines |
Understanding Oil Viscosity
🌡️ Temperature Effect
Viscosity drops when heated. Water: 1.8 cP at 0°C → 0.28 cP at 100°C. Oil changes even more dramatically.
🛢️ SAE Grades
"W" = Winter. First number: cold viscosity. Second: hot viscosity. 5W-30: flows at -30°C, behaves as SAE 30 when hot.
📊 Viscosity Index (VI)
Measures temperature stability. Higher VI = less change with temperature. Modern synthetics: VI 150+. Mineral oils: VI 80-120.
⚖️ cP vs cSt
cP = dynamic (absolute). cSt = kinematic (cP ÷ density). For water-like fluids (ρ≈1): cP ≈ cSt.
Frequently Asked Questions
What is the viscosity of water?
1.002 centipoise at 20°C. Varies with temperature: 1.79 cP at 0°C,
0.65 cP at 40°C, 0.28 cP at 100°C. Used as reference point for viscosity.
What is centipoise?
1 cP = 0.001 Pa·s = 1 mPa·s. Most common viscosity unit. Water ≈ 1
cP at 20°C. Honey ≈ 2,000-10,000 cP. Named after Poiseuille.
How does temperature affect oil viscosity?
Viscosity decreases as temperature increases. Motor oil: ~150 cP
at 40°C → ~20 cP at 100°C. This is why multi-grade oils (5W-30) are designed to work across temperature
ranges.
What do SAE oil grades mean?
SAE = Society of Automotive Engineers. Numbers indicate viscosity.
"W" = Winter (cold performance). 5W-30: pumps at -30°C, viscosity of SAE 30 when hot.
What is the viscosity of motor oil?
Varies by grade and temperature. SAE 30 at 40°C: ~100-110 cSt. SAE
5W-30: ~60 cSt at 40°C, ~10 cSt at 100°C. Check your engine manufacturer specifications.
What is the viscosity of glycerin?
~1,500 cP at 20°C. Much more viscous than water. ~630 cP at 40°C.
Used in food, cosmetics, pharmaceuticals.
What is the viscosity of heavy oil?
200-10,000+ cP depending on type. Heavy crude oil: ~200-2,000 cP
at 20°C. Bitumen: 100,000+ cP. Must be heated for pumping.
How do I convert poise to centipoise?
Multiply by 100. 1 P = 100 cP. 1 P = 0.1 Pa·s. Poise is CGS unit;
centipoise more practical for most fluids.
How do I convert cP to Pa·s?
Divide by 1000. 1 cP = 0.001 Pa·s = 1 mPa·s. Example: water (1 cP)
= 0.001 Pa·s.
What is viscosity index (VI)?
Measures how viscosity changes with temperature. Higher VI = more
stable. 0 = naphthenic oil baseline. 100 = paraffinic. Modern synthetics exceed 150.
Why is cold viscosity important for motor oil?
Affects cold starting. Oil must pump to engine quickly on cold
start. Too thick: poor protection during first minutes. That's why winter-rated oils (5W, 0W) matter in
cold climates.
What is the difference between cP and cSt?
cP = dynamic viscosity. cSt = kinematic
viscosity. cSt = cP ÷ density. For fluids with density ≈ 1 g/cm³ (water), cP ≈ cSt.
What viscosity oil should I use?
Follow manufacturer recommendation. Modern engines: often 0W-20 or
5W-30. Older engines: 10W-40. Check owner's manual. Using wrong viscosity can damage engine or void
warranty.
How is oil viscosity measured?
Viscometers: Capillary (Saybolt), rotational (Brookfield), falling
ball. SAE grades use specific test conditions: cold cranking simulator (-18°C), high-temp high-shear
(150°C).
What is Newtonian vs non-Newtonian fluid?
Newtonian: constant viscosity (water, oil).
Non-Newtonian: viscosity changes with shear (ketchup, paint, blood). Multi-grade oils
use polymers that are somewhat non-Newtonian.
Why does honey flow slower when cold?
Higher viscosity at lower temperature. Honey: ~2,000 cP at 25°C →
~10,000+ cP at 10°C. Warming honey reduces viscosity, making it pour easier.
How accurate is this viscosity converter?
Uses standard conversion factors. Fluid viscosity values are
typical reference values; actual viscosity depends on exact composition, temperature, and shear rate.