MAC(Alter, Gas)=MAC(40, Gas)*10^
(-0,00269*(Alter-40))

MAC(AGas, N2O)=(Konz AGas et/MAC(Alter, AGas))+(Konz N2O et/MAC(Alter, N2O))

MAC(40):
Halothan 0,77%
Enfluran 1,70%
Isofluran 1,15%
Desfluran 6,65%
Sevofluran 2,10%
N2O 105%

Modern anaesthesia machines calculate the MAC according to the above formula for one other gas +/- N2O. As it is quite a complicated formula it would be handy to only have to put in
age
endtidal gas 1
endtidal gas 2
endtidal N2O

into MedCalc to get the combined MAC value when you have to use a machine that doesn't.

Oh and it would be nice not only to be able to calculate the standard MAC but also the MAC(aware), the average anaesthetic concentration at which 50% of patients regain awareness. So far I couldn't find MAC(40,aware) values though.

I disagree. I don't find this an useful formula.
Since we have gas analysers, the MAC values are not really that important.
The skilled anesthesiologist who trained with gasman and studied the gasses properly wouldn't need such a formula, thus it would represent very little benefict in practical life.
For such data, I would recommend the app gas guide- it has all these values. It is quite handy to first year-anesthesiology residents such as myself. =)
Cheers!

Yes! Implementing "Nomogram to estimate age-related MAC" (http://www.ncbi.nlm.nih.gov/pubmed/15220181) as a MedCalc formula would be great! It would be so much more convenient to type a couple of values into MedCalc than mess around with rulers and drawing lines.

It should have the option to input age and end-tidal agent concentration with an output of MAC value, or input age and desired MAC value with an output of end-tidal agent concentration. And the advantage of a formula rather than a nomogram is that you could input any concentration of nitrous oxide, rather than being limited to 0%, 50% and 67% as the nomogram is.