Scale a sauce recipe to your desired batch yield.
Scaling a sauce is two separate calculations. The multiplier is simply target yield over original yield, and it applies directly to every ingredient by weight. The volume you must start with is a different figure, because simmering drives off water: to finish with 2400 ml after losing a quarter you have to begin with about 3200 ml. Getting this backwards is why scaled sauces so often come out short or too thin. One caveat the multiplier does not capture — reduction rate depends on surface area, so a large batch in a wide pan reduces faster than the recipe expects and needs the heat and timing watched.
Recipe multiplier
Multiplier = target yield / original yield
Starting volume
Starting ml = target yield / (1 - reduction%)
Simmering evaporates water, which is how a sauce thickens and concentrates. If you want 2400 ml in the jars and expect to lose 25 percent, you must start with about 3200 ml. Scaling ingredients to the target volume alone leaves you a quarter short.
Bulk ingredients do. Salt, chilli, strong spices and thickeners often do not — perception is not linear and a quadrupled batch can taste harsh at four times the seasoning. Scale those to about 75 percent initially, then taste and adjust at the end when the sauce is at final concentration.