Recipe Rescaler
Scale a recipe from whatever you actually have. Not just "serves 4 → serves 6" — pick any ingredient, say how much of it you are using, and everything else follows. Switch the whole thing between metric and cups while you are there.
Import a recipe from a web page
Reads only the ingredient list, the title and the serving count, from the structured data the page already publishes for search engines. The method is not imported — follow the link back for that. Nothing is stored, and if a page does not publish its recipe in a readable form you will be told to paste instead.
Step 2 — what are you scaling to?
Measure in
Your recipe
Weights and volumes are converted per ingredient using USDA FoodData Central densities — a cup of flour is 125 g and a cup of sugar is 200 g, so there is no single conversion factor to apply. Anything the tool could not identify keeps the unit the recipe gave it.
Why scaling a recipe is not just multiplication
Pick the ingredient you are actually constrained by
Most scalers only ask how many servings you want, which assumes the serving count is what is fixed. Usually it is not. What is fixed is the three-quarters of a cup of sugar left in the bag, the four eggs in the door of the fridge, or the 400 g tin you have already opened. Scaling from that is the same arithmetic pointed the useful way round.
Eggs are the awkward one
Two thirds of a six-egg custard is four eggs, which is tidy. Half of a three-egg cake is not. Beat the odd egg and weigh out what you need — a large egg is about 50 g without its shell, roughly 17 g of yolk to 33 g of white. It matters in a custard and it does not in an egg wash.
Leaveners and time do not follow the factor
Baking powder and bicarbonate stop scaling linearly somewhere around double, because a bigger batch holds on to gas more efficiently; past that point use about three quarters of the calculated amount. Cooking time never scales at all — it follows the depth of the food and the surface area of the tin, not the total quantity.