"dilatation isobare" is "isobaric expansion". (For some explanation, see, eg page 2 of http://physics.usask.ca/~plyukhin/ep271/assignments/sol9.pdf...
The term coefficient can be added to this compound - but isobaric expansion coefficient is rarely used. As explained in the pdf file above, the isobaric expansion follows the very simple law
T/V (temperature divided by volume) = constant, so if you need to know the final volume, V_f, you get it by V_i x (T_f/T_i), where the subscripts refer to f(inal) and i(initial). T_f/T_i is just the ratio of the two temperatures, measured in Kelvins. If temperature is measured on the Fahrenheit or the Celisus scale, the formula is a bit more complicated - and in that case isobaric expansion coefficient makes sense.

I would use "calculation" (in singular) for "calcul", since it is just derivation leading to a result.