The interpolation calculator provided below is used to determine:
- the kinematic viscosity values, depends from temperature, calculated by the formulas specified in ASTM D341 – (‘Standard Practice for Viscosity-Temperature Charts for Liquid Petroleum Products’);
- the Viscosity Index (VI) by the formulas specified in ASTM D2270 (`Standard Practice for Calculating Viscosity Index from Kinematic Viscosity at 40 and 100°C 1`) or in ISO 2909 (`Standard Practice for Calculating Viscosity Index from Kinematic Viscosity at 40 and 100°C 1`) or in ГОСТ 25371-2018 (`Нефтепродукты. Расчёт индекса вязкости по кинематической вязкости`)
Any mineral oil is supplied with the specification of kinematic viscosity values at two different temperatures, usually at 40°C and at 100°C (or at 100°F and at 210°F). These data is enough to determine kinematic viscosity at any other values of temperature and as well Viscosity Index.
You can calculate pre-filled values of oil classified by ISO 3448 with grades VG22, VG32, VG46 or VG68 (at viscosity Index = 100) or enter specific values for any other oils.
The calculator below is for informative purposes only. The use of any of the calculators’ results is at the user’s sole risk.
How to use calculator
Just put your values (either imperial or metrical) in the appropriate fields below and press ENTER. All other values will be re-calculated automatically. The graphic curve will be updated as well.
|Select hydraulic oil:|
|Kinematic viscosity at Temperature #1||cSt||SUS|
|Kinematic viscosity at Temperature #2||cSt||SUS|
|Temperature to calculate||°C||°F|
|Kinematic viscosity at calc. temperature||cSt||SUS|
by ISO 2909:2002 Procedures A and B
by ASTM D2270-04 Procedures A and B
by ГОСТ 25371-2018 Методы А и Б
If you find some mismatch or an error or just have any questions please do not hesitate to leave your comments below.
OUR FUEL VISCOSITY IS 39.9MM AT 50 DEG C
I WANT VISCOSITY OF 18MM2 AT BOILER WHAT WILL BE TEMPERATURE TO MAINTAIN THAT VISCOSITY.
Hello Ali. I assume when you say 39.9MM and 18MM2 you mean viscosity 39.9mm^2/s and 18mm^2/s what are equivalents to 39.9 cSt and 18.0 cSt accordingly. Unfortunately, it means you have oil with the custom grade and just one parameter of viscosity at temp is not enough to make this calculation in accordance with the standard. Please check your oil specification – there should be two lines of viscosity at temp. Put them in the table above and find the value of temp at any value of viscosity.
Thank you very much for making it available to everybody!
thank you very much for your effort.
is this calculator applicable to another oil type (engine, gear, etc)?
Thanks for your feedback! This chart uses equations as per ASTM D341 standard to calculate relationship temp-visc for any liquid petroleum products and lubricants.
hey , given viscosity of 1000 cSt at -20 deg C , and ASTM slope of 0.6 , how to find VI?
GREAT TOOL GOO JOB!!!
I am using a SAE 75-90 wt synthetic gear oil. I am needing to find out viscosity as per temperature – viscosity chart in reyn. Can you help me how I can do it.
Hello! Reyn is a British unit of dynamic viscosity. This chart is for kinematic viscosity extrapolation.
Hi, Great work!
The ASTM D341 states that it’s possible to use 3 points for the extrapolation. Do you know how this could be achieved?
hello Thomas. Thanks for you comment.
Standard D341-03, paragraph 1.1:
“1.1 The kinematic viscosity-temperature charts (see Figs. 1
and 2) covered by this standard are a convenient means to
ascertain the kinematic viscosity of a petroleum oil or liquid
hydrocarbon at any temperature within a limited range, pro-
vided that the kinematic viscosities at two temperatures are
So, like you see this standard for the extrapolation using 2 points. Sorry, I didn’t find any states about 3 points in this standard, did you?
And… what is the sense to make a calculator for 3 points if all oil manufacturers provide temp/visc parameters for their oil only for 2 points?
My lubricant is SAE 20W-40 at 60 °C, what would be its absolute viscosity in mPa. s
For ISO VG 100 oil, how to find constants A&B
using Walther-ASTM equation to determine the
effect of temperature on viscosity of the oil as per the
parameters given below.
a. Temperature range (273 – 523 K)
b. Kinematic viscosity: 99.4 cSt at 40 C and 11.12 cSt at 100 C.
and Show the relationship between viscosity (vertical)
and temperature (horizontal) of ISO VG 100 oil
using a graph and discuss the results as the
please any one answer this question?
Would it be possible to list the A & B Constants for the oils in the chart? I’m trying to do an Excel calculation with a curve fit based on the data points in the tool but it is not accurate enough. I’d like to use the equations directly but I don’t know where to get the A and B constants.
Would you be able to send me the excel file so i can create graphs using andrade equation?
How is it calculated?
I do not have an Excel file, the kinematic viscosity values are calculated by the formulas specified in ASTM D341 – (‘Standard Practice for Viscosity-Temperature Charts for Liquid Petroleum Products’).
Hi Dzyanis, I really love this tool and it’s helped me to understand both VI and the relationship between viscosity and temperature in a way that other explanations have not. I think this is great for those of us that lack your engineering knowledge and experience.
I have one suggestion. It would be really great, if you could input TWO different oil products, and have them both charted on the same graph with the the x/y scaling fixed to whichever is the larger data range. With two lines showing overlapped, you could make very convincing visual comparisons between TWO different oil products.