How do I scale a recipe up or down for a different number of people?
Multiplying every ingredient by the same factor works for simple dishes such as soups, stews or sauces, but it falls apart with baking. A cake written for a 20cm tin does not simply double when you move to a 25cm tin, because the volume of a round tin increases with the square of the radius, not in a straight line. Bake time changes too: a thicker layer needs longer in the oven but at a slightly lower temperature, or the edges will dry out before the centre sets.
Leavening agents are the other trap. Baking powder and yeast do not always scale proportionally once a batch gets much larger or smaller, since rise time depends on dough depth and surface area as well as quantity. Salt and spices are usually safer to scale down slightly for large batches, since strong flavours can feel overpowering once concentrated across more portions.
Rather than reaching for a calculator and a pan diameter chart, entering your original recipe and target servings gives you adjusted quantities in one step, including pan size corrections for baked goods.
What can I use if I am missing a baking ingredient?
Running out of eggs, butter or buttermilk mid recipe does not have to mean a trip to the shop. Some ratios that hold up well in most bakes: one egg can be replaced with about 60ml of unsweetened apple sauce or a mashed banana in cakes and muffins, though the result binds slightly less well than a real egg. No buttermilk? Stir a tablespoon of lemon juice or white vinegar into 250ml of ordinary milk and let it sit for five minutes.
Self-raising flour can be made from plain flour by adding 2 teaspoons of baking powder per 150g, a common fix in UK kitchens where recipes often specify one or the other without warning. Butter can generally be swapped for the same weight of neutral oil in quick breads, though the crumb will be denser and less flaky than with butter.
Not every swap works in every recipe, and ratios shift depending on what else is in the bowl, so it helps to check a substitution against the specific ingredient you are missing before committing a whole batch to it.
How do I actually read the numbers on a nutrition label?
UK packaging typically lists values per 100g alongside a per portion column, and the two tell different stories. Per 100g lets you compare two products fairly regardless of pack size, which is the figure the traffic light colour coding on the front of UK packs is based on. The per portion figure only matters if the stated portion size matches what you actually eat, and it often does not.
Calories from fat, carbohydrate and protein are not interchangeable even at equal gram counts: fat carries roughly 9 calories per gram, while carbohydrate and protein carry about 4 each. A product low in fat can still be high in sugar, which sits inside the carbohydrate figure rather than as a separate warning.
Working out a full meal from several packaged ingredients by hand is slow and easy to get wrong. Entering each item's label values totals the meal automatically.
How long does food actually stay safe to eat after opening or cooking?
The UK Food Standards Agency draws a clear line between a best before date and a use by date. Best before is about quality, not safety: food past that date may lose flavour or texture but will not necessarily make you ill. Use by is a safety cut-off, mainly applied to chilled foods such as meat, fish and dairy, and food should not be eaten once that date has passed, even if it looks and smells fine.
Cooked leftovers follow a separate rule of thumb: cool within two hours, refrigerate, and eat within two to three days. Freezing pauses the safety clock but not quality, so freezer-burnt food is still safe, just worse to eat. Because these limits vary by food type and storage method, a single memorised rule rarely covers everything in a fridge.