Recipe authors often use metric units for accuracy and consistency, as grams and milliliters measure mass and volume directly, unlike cups and spoons which can vary significantly depending on packing and technique. This is especially important for dry ingredients where volume measurements can be highly inconsistent.
The primary reason recipe authors prefer metric units is precision. Grams (g) and milliliters (mL) are units of mass and volume, respectively. When you measure 100g of flour, you're getting a specific mass of flour, regardless of how finely it's ground or how much it's settled. Similarly, 50mL of water is a defined volume.
Cups and spoons, on the other hand, are volume measurements that are highly susceptible to variation. The amount of flour in a cup can change dramatically depending on whether you scoop it directly from the bag (which compresses the flour) or spoon it lightly into the cup. This difference in packing density can lead to significant discrepancies in the final recipe outcome.
For dry ingredients, this issue is particularly pronounced. A cup of packed brown sugar will weigh significantly more than a cup of lightly spooned flour. This inconsistency makes it difficult to replicate recipes accurately when using volume measurements.
Wet ingredients are less prone to these variations, but even then, slight differences in measuring techniques can affect the final result. Using metric units eliminates these ambiguities, ensuring that everyone uses the same amount of each ingredient, leading to more consistent and predictable results. Many bakers find that using a kitchen scale improves their baking dramatically.
When converting from metric to US customary units, always double-check the conversion factors, especially for dry ingredients. Different sources may provide slightly different conversions, and using the wrong conversion can throw off your recipe. Using an online conversion tool is a great way to ensure accuracy.