Doubling a recipe by doubling every number works less often than people expect, and the failures are systematic rather than random.
The conversions themselves scale linearly. If a cup of flour is 120 grams, two cups is 240 grams. Nothing surprising there, and this is the part that makes scaling feel safe.
What does not scale linearly is everything around the ingredients. Pan surface area grows faster than depth, so a doubled batter in the same-sized tin cooks differently. Evaporation depends on exposed surface, not volume. Leavening interacts with batter mass in ways that are not proportional. Seasoning is perceptual rather than arithmetic.
The practical approach is to scale by weight rather than volume, because weight is the one axis that genuinely is linear, and then treat time, temperature and pan size as separate decisions rather than derived ones. Converting to grams first also removes the compounding rounding error you get from scaling fractional cup measures, where a third of a cup times 1.5 becomes an awkward number that gets rounded twice.
Convert first, scale second, and re-think the pan.
Ingredient conversion and scaling: ingredientcalculator.com