One question I get often revolves around measuring by weight or volume. I love this questions and I hope I can convince everyone to start weighing their ingredients.
Let's jump back first to the old school American way of measuring. You pull out a cup that says the measurement, take a scoop, level it, and use it. This has worked for American families for years, but as we moved into technology and recipes weren't just something passed from parent to child, more complications arise. If you learn from your grandmother, you will see how she scoops the flour and measures the other ingredients. Does she scoop from a bag? Maybe she has a container that she uses but always fluffs the flour before taking a scoop. Or the classic sifting to incorporate air and lighten the load. Without knowledge of exactly how the ingredients are measured there is so much room for more or less to be used and to change the results.
Not only is there the issue of how to measure there's also the definition of a cup. What is 1 cup? In the U.S. we have two types. The legal cup used for nutritional purposes is defined as 240ml. (check out the link below for the FDA guideline) The legal cup is used in all science based operations with packaging, labeling, medicine, things were you can get in trouble for mistakes. We also have a customary cup that is the common cup. This measurement is used in most home use and is defined to equal 236ml. A small difference but when you're looking at a recipe with 7 cups of flour that is a variance of 28ml and that will have an effect on a recipe.
Not only do we have two types of cups in the U.S. there are also international cups. We have the Metric cup (250ml), the Canadian cup (227ml), the UK cup (284ml), the Latin cup (this one varies by nation between 200ml-250ml), the Japanese cup (200ml), and even a Russian cup (123ml). When we look at recipes in modern times we go online and find what we want, but we can't trace the recipes half the time or exactly what measurement is used. Plus we don't know how that person measured their ingredients. Did they fluff the flour? Did they sift? Are they leveling with a knife? Maybe a finger? Maybe they just shake the measuring cup and let it level itself.
OR JUST WEIGH EVERYTHING. Everywhere on this planet 1 pound is going to weigh 1 pound, 1 kilo will be 1 kilo. (although I do recognize there can be slight difference and anomalies throughout our planet.) Until the day we travel to other planets and gravity levels shift, we can depend on the weights used here. No matter how to scoop your flour, if it's fresh and fluffy or old and dense, you can always get the right measurement. So please, buy a scale (even a cheap $20 one) and start weighing your ingredients. You will be so happy with how consistent and better your baking will become.