Quick viscosity reference
Find an Oil Viscosity Grade
An ISO VG grade indicates an industrial oil’s nominal kinematic viscosity at 40°C. For example, ISO VG 46 = 41.4–50.6 cSt at 40°C. Engine-oil labels such as 5W-30 use a different grading system.
Find ISO VG grade from a viscosity measurement
Use measured kinematic viscosity at 40°C (not at 100°C).
46 cSt at 40°C falls within ISO VG 46 (41.4–50.6 cSt). This classifies viscosity only, not lubricant suitability.
cSt = mm²/s. ISO VG is a viscosity classification, not a viscosity-index, oil chemistry or equipment-approval designation.
Industrial and hydraulic oil · ISO 3448
ISO VG Oil Viscosity Chart (at 40°C)
These are standardized 40°C kinematic-viscosity limits. The letter/number is a grade label, not the oil’s viscosity at arbitrary operating temperatures.
No listed ISO VG grade matches this search.
| ISO VG grade | Minimum (cSt) | Nominal (cSt) | Maximum (cSt) |
|---|---|---|---|
| ISO VG 2 | 1.98 | 2.2 | 2.42 |
| ISO VG 3 | 2.88 | 3.2 | 3.52 |
| ISO VG 5 | 4.14 | 4.6 | 5.06 |
| ISO VG 7 | 6.12 | 6.8 | 7.48 |
| ISO VG 10 | 9 | 10 | 11 |
| ISO VG 15 | 13.5 | 15 | 16.5 |
| ISO VG 22 | 19.8 | 22 | 24.2 |
| ISO VG 32 | 28.8 | 32 | 35.2 |
| ISO VG 46 | 41.4 | 46 | 50.6 |
| ISO VG 68 | 61.2 | 68 | 74.8 |
| ISO VG 100 | 90 | 100 | 110 |
| ISO VG 150 | 135 | 150 | 165 |
| ISO VG 220 | 198 | 220 | 242 |
| ISO VG 320 | 288 | 320 | 352 |
| ISO VG 460 | 414 | 460 | 506 |
| ISO VG 680 | 612 | 680 | 748 |
| ISO VG 1000 | 900 | 1000 | 1100 |
| ISO VG 1500 | 1350 | 1500 | 1650 |
Classification bands do not cover every possible measured viscosity—values in the gaps between grade bands may match no grade. Smaller classes ISO VG 2/3/5/7 use standard midpoint values of 2.2, 3.2, 4.6 and 6.8 cSt respectively. ISO 3448 source.
Motor oil · SAE J300
SAE Engine Oil Viscosity Chart: 0W-20, 5W-30, 10W-30 and 5W-40
The second number in an engine-oil multigrade specifies a hot-viscosity grade, measured in part at 100°C. The W grade is based on separate cold-temperature tests. A 5W-30 label is not a cSt reading or an ISO VG grade.
| SAE hot grade | 100°C viscosity (cSt) | Common multigrade example |
|---|---|---|
| SAE 8 | 4.0 to <6.1 | Specialty low-viscosity grades |
| SAE 12 | 5.0 to <7.1 | Specialty low-viscosity grades |
| SAE 16 | 6.1 to <8.2 | 0W-16 |
| SAE 20 | 6.9 to <9.3 | 0W-20, 5W-20 |
| SAE 30 | 9.3 to <12.5 | 5W-30, 10W-30 |
| SAE 40 | 12.5 to <16.3 | 0W-40, 5W-40, 15W-40 |
| SAE 50 | 16.3 to <21.9 | 20W-50 |
| SAE 60 | 21.9 to <26.1 | SAE 60 |
Important: These hot-grade kinematic viscosity intervals alone do not establish SAE compliance. The full specification also has HTHS viscosity and, for W grades, cold cranking and pumping requirements. SAE 8/12/16 low-viscosity bands overlap at some 100°C values, so a single test result cannot always determine a grade. Always use the OEM-required oil.
Specific oil · two measured data points
Oil Viscosity vs. Temperature Calculator
Enter two kinematic viscosities for the same oil (often the product datasheet values at 40°C and 100°C). The ASTM D341-style Walther relationship estimates viscosity between those temperatures—not from an ISO VG number alone.
Find temperature for a target viscosity
Enter a viscosity within your two known values for a temperature lookup.
Calculated Viscosity–Temperature Curve
Horizontal: temperature. Vertical: kinematic viscosity (log scale).
The curve is calculated only from the entered measurements. It is not an ISO VG-typical oil curve, a viscosity-index measurement, or an OEM lubricant recommendation.
How to Read Oil Viscosity Charts
Industrial oil classification: ISO VG 68 covers 61.2–74.8 cSt at 40°C, not at every temperature.
For 5W-30, 5W relates to low-temperature tests and 30 to hot-grade requirements, including a 100°C kinematic-viscosity interval.
cSt (mm²/s) measures kinematic viscosity. cP (mPa·s) measures dynamic viscosity; density at the same temperature is needed to convert between them.
VI describes how much viscosity varies with temperature. Two oils with the same ISO VG grade can have different 100°C viscosities and different VI.
What does the viscosity–temperature curve show?
For most petroleum lubricants, kinematic viscosity decreases as temperature rises. The calculator plots only the range between two measured values. A different oil with the same viscosity at 40°C can follow a different curve.
ASTM D341 calculation method
The Walther transformation is written as log₁₀(log₁₀(ν + 0.7)) = A − B log₁₀(T), where ν is kinematic viscosity in cSt, T is absolute temperature in kelvin, and A and B are determined using two viscosity measurements. This simplified form is used here only for lubricating-oil viscosities of at least 2 cSt.
Given 70 cSt at 40°C and 10 cSt at 100°C, estimated viscosity at 70°C ≈ 22.32 cSt. This is interpolation, not a recommendation to use that oil in any particular machine.
Choosing Oil Viscosity for a Machine
- Start with the OEM specification. Check the prescribed ISO VG or SAE grade, additive chemistry, applicable approvals, and viscosity window at operating temperature.
- Identify the oil type. Hydraulic, compressor, turbine, gearbox and engine oils may require different chemistry even when their cSt readings match.
- Use actual datasheet values. Obtain viscosity at 40°C and 100°C (or two defensible temperatures) for the specific product.
- Check cold-start and hot-running needs. The correct oil must be suitable for the intended operating conditions.
Do not choose a replacement from an ISO-to-SAE numeric comparison alone. The tables are reference classifications, not substitute-product recommendations.
Oil Viscosity Chart FAQ
What does ISO VG 46 mean?
ISO VG 46 means an industrial oil’s 40°C kinematic viscosity falls between 41.4 and 50.6 cSt. It does not describe the entire temperature curve or lubricant additive package.
What is the oil viscosity of 5W-30 at 100°C?
The SAE 30 hot grade corresponds to 9.3 to less than 12.5 cSt at 100°C. A 5W-30 must also satisfy the 5W cold-temperature requirements and applicable high-temperature high-shear limits. The exact 100°C value is product-specific.
Does ISO VG 68 equal SAE 20 or SAE 30?
No exact correspondence exists: ISO VG is defined at 40°C, whereas SAE J300 is an engine-oil rheological specification involving multiple tests. Never substitute solely on grade-label similarity.
What is the difference between cSt and cP?
cSt is kinematic viscosity; cP is dynamic viscosity. A conversion requires density at the same temperature: cP = cSt × density in g/cm³.
Does a higher ISO VG number mean thicker oil?
At the common 40°C reference temperature, a higher ISO VG midpoint indicates a higher nominal kinematic viscosity. This does not automatically make it the correct lubricant for the machine.
Why does oil viscosity change with temperature?
Most liquid petroleum oils flow more readily when warmer; their resistance to shear decreases as temperature rises. The exact rate of change depends on oil formulation and viscosity index.
Can I calculate an oil’s viscosity at 80°C from ISO VG 46 alone?
No. An ISO VG number is a band at 40°C, not a temperature curve. You need measured viscosity at two temperatures for the same oil, or suitable manufacturer data.
Standards, Sources & Calculation Scope
Published references checked October 2026. Selected ISO VG values and SAE viscosity bands are reference facts, not a reproduction of complete proprietary standards. Always use the actual applicable standard or OEM specification in controlled engineering work.
- ISO 3448:1992 — Industrial liquid lubricants, ISO viscosity classification. 40°C viscosity-grade midpoint and minimum/maximum reference ranges; ISO lists the standard as current, confirmed in 2023.
- ASTM D341-20(2025) — Viscosity–temperature equations and charts. Method scope for estimating viscosity from two known measurements over a limited temperature interval; this tool uses only the simplified ν+0.7 Walther form above 2 cSt.
- SAE J300_202405 — Engine oil viscosity classification. Rheological classification; hot-grade values summarized in limited form from manufacturer resources.
- FUCHS — SAE viscosity charts. Public hot-viscosity grade-band comparison including 100°C viscosity limits.
- SAE J306_202502 — Automotive driveline lubricant viscosity classification. Establishes distinct gear-oil scope, not a direct SAE-engine/ISO equivalence.
Scope limitations: no extrapolation, no viscosity-index calculation, no low-viscosity ASTM correction below 2 cSt, no engine-oil cold-test calculator, no flash/pour-point prediction and no implied OEM approval.