Why can't I convert cups to grams with one fixed number?
Because cups measure volume and grams measure mass, and the relationship depends entirely on density. A cup of flour is about 120–125 g, a cup of granulated sugar about 200 g, and a cup of water 240 g — all the same volume. Any converter offering a single cup-to-gram figure is only correct for one ingredient. This is why serious baking recipes give weights.
Why do professional bakers weigh instead of measuring cups?
Because volume measurement of dry goods is unreliable. Scooping flour straight from the bag compacts it and can yield 20% more than spooning it in and levelling off — enough to turn a tender cake dry. Weight removes that variable entirely, which is why it is standard in professional kitchens and in most European and Australian recipes. A digital scale is the single biggest accuracy upgrade in home baking.
Is a US cup the same as a metric or imperial cup?
No, and the differences matter in baking. A US customary cup is 236.6 ml, a US legal cup (used on nutrition labels) is 240 ml, a metric cup is 250 ml, and an old imperial cup was 284 ml. Australian tablespoons are 20 ml where US and UK tablespoons are about 15 ml. A recipe from an Australian source using four tablespoons of butter gives noticeably more than a US one.
How do I scale a recipe up or down?
Multiply the ingredients by your factor, but do not scale everything blindly. Leavening agents, salt and strong spices often need less than proportional increases — doubling a cake usually needs slightly less than double the baking powder. Pan size and baking time do not scale linearly at all: a doubled batter in a deeper tin needs a longer, cooler bake. Cooking time is governed by geometry and heat transfer, not by quantity.
How should I convert oven temperatures?
Fahrenheit to Celsius is (F minus 32) times 5/9. Beyond the arithmetic, fan or convection ovens typically run 15–20 °C hotter in effect, so recipes usually advise reducing the set temperature by that much. Gas marks are a separate scale again — gas mark 4 is roughly 180 °C or 350 °F. Ovens also routinely misreport by 10–20 degrees, so an oven thermometer is worth more than a precise conversion.
Does it matter whether butter is measured melted or solid?
Yes, for volume measurements. A cup of solid cubed butter contains air gaps; melted butter fills the cup completely, so you get more fat. Recipes calling for melted butter measured after melting differ from those measuring solid then melting. Weight sidesteps the problem: 113 g is 113 g in either state. The same applies to packed versus loose brown sugar, where the difference can be 30% or more.