I cook with metric recipes sometimes and once you learn a small handful of conversions it is pretty easy. Most things are going to be either cups teaspoons or tablespoons so if know a cup is 250m, a tablespoon is 15ml and a teaspoon is 5ml then you will only need a chart every once in a while. You don't have to be exact so the math is easy. 50ml really isn't 1/4 cup but it is close enough for most things. A quart isn't equal to a liter but if you are talking about how chicken stock to add it is probably close enough.