Determine formula for calculating values in a table.

Is there a way to calculate the relationship between a set of values?

When I see a question like this, my first thought is to use curve fitting/regression. I don't know how familiar you are with regression techniques -- it might be worth visiting your favorite intro to stats text and review linear regression techniques.

In Excel, I find the easiest way to curve fit data is to use the LINEST() function http://office.microsoft.com/en-us/ex...in=HA010277524

Often the hardest part of curve fitting is deciding what form of equation to use. This will usually be based on your knowledge of the underlying physical process being modeled and the expected equation that should use.

Your data look fairly linear, without more information I would suggest a simple straight line y=mx+b, for which examples are readily given in the help file.

Once you have the equation and the parameters for the equation, it should be easy to create a block of cells where you can input any T and get any P.

A 5 parameter polynomial will provide a better fit than a 2 parameter polynomial any day of the week. The difficult part is justifying those extra parameters.

Whenever I end up needing a high order polynomial like that to fit my data, I wonder if there is a better choice of equation. For example, most of the time when I want to relate temperature and pressure, the data I get usually needs some kind of exponential equation (depending, of course, on what physical properties were measured). A polynomial will require 4 or more parameters to fit data that could easily be fit by a 2 parameter exponential equation. I guess my point is, it might be worth the effort to do a little research and see if there is something better than polynomials to fit your data.

he equation isn't giving me exactly the right #s,

In what way is it not giving you exactly the right numbers? As noted, perhaps a different choice of equation would be better. Or perhaps a completely different approach. Another approach I use for this sort of thing is linear interpolation. Unfortunately, Excel does not have a built in linear interpolation function, but they are easy enough to build. If you search the forum, there have been UDF's proposed for linear interpolation -- one of them may suit your problem.