I have a recipe that calls for 5 pounds of flour, but I live in a country that sells their flour in 1-kg bags. So I put in 2 kg = 4.4 pounds... How many cups should I put in for the remaining .6 pound that I'm missing?
The weight of flour varies immensely depending on how densely it's packed and the humidity. If you've started with a weight-based recipe, I'd try to find a scale.
If that's absolutely not an option, I tend to approximate 100g = 1 cup.
Be warned, I've found some recipes that are really sensitive to the amount of flour and the difference between a lightly sifted cup and a scooped cup can really throw off the results. You might do better to try to divide another kg package of flour evenly and use the approximation that 0.6 lb is about 0.25 kg (i.e. one quarter of the bag).
According to Wolfram-Alpha, 1cup of flour weighs 137g. 0.6lb is 272g, so about 2 cups.
it's actually even more complicated than that! different TYPES of flour weigh differently. a cup of all-purpose will weigh differently than a cup of bread flour, and both will weigh something different from a cup of unbleached white flour (and then there's wheat flour...). i tend to trust the weight per serving on the nutritional information panel, and calculate the weight per cup from that.