Main Jet Calculator
Find it in operation at: http://mitchellwaite.ca/MainJetCalculator/
This calculator is essentially a linear interpolation of carburetor jet conversion charts found online. It will give you a good main jet to start when tuning a carburetor for a new altitude or temperature range.
The chart data was analyzed in excel to determine an approximate formula for the jet correction factor. The results are available in
JetCharts.xlsx. There's an R^2 value of 0.991, and the residual plots don't seem to show any bias.