This should automatically update whenever you change any of these fields. I've only tested it in firefox though, so I apologize if it doesn't work in whatever browser you're using.
If you'd rather use a unit other than ounces, just pretend it says what you want instead of "oz." I only put ounces there because it looked weird with no given unit.
If you're unsure about what values to give, here's a table of values that I basically got from wikipedia. If you're trying for something specific, you'll likely want to do your own research :-)
| Dairy | % butterfat |
|---|---|
| Skim milk | <0.5% |
| Low fat milk | 1% |
| Reduced fat milk | 2% |
| Whole milk | 3.25% |
| Half and half | 12% |
| Single/Table cream | 24% |
| Whipping cream | 36% |
| Double cream | 48% |
| Devonshire cream | 55% |
| Butter | 80% |
If you want the fractions to be less specific, you can control that here:
(If clicking one of these boxes appears to have no effect, try clicking somewhere else on the page right after.)