Why they're all 1:1, but not all equal
Every plant-based milk is formulated to pour and measure like dairy milk, so volume-for-volume substitution always works — you'll never need to adjust the amount itself. What does vary is protein and fat content, both of which matter more in baking than in something like coffee or cereal. Dairy milk's protein helps baked goods brown and set structure; a plant milk lower in protein can bake up slightly paler and softer. None of this makes a substitute "wrong" — it just shifts the result a little, more noticeably in delicate bakes than in something like pancakes or a basic quick bread.
Which one to reach for
Soy milk is the closest match to dairy milk's protein content, making it the most reliable choice specifically for baking where structure matters. Oat milk is naturally a little sweet and creamy, a good all-purpose choice for both baking and drinking. Almond milk is thinner and lower in protein and fat than the other options, fine for most everyday uses but the least structurally similar to dairy milk. Carton coconut milk (not the thick canned kind, which is far too rich) adds a mild coconut flavor and a bit more richness than the others.
FAQ
Should I use unsweetened versions? Yes, for baking and cooking — sweetened plant milks add sugar the original recipe didn't account for, which can throw off both sweetness and browning.
Do these substitutes work in a recipe that also uses buttermilk? Not directly — buttermilk's acidity plays its own role. Add a tablespoon of lemon juice or vinegar per cup of any plant milk here to approximate that acidity if a recipe calls for buttermilk specifically.
Is evaporated milk + water the same kind of substitute as the others? Not quite — it's a pantry-emergency swap (you're out of regular milk but have a can of evaporated milk on the shelf), not a dietary one, since evaporated milk is still dairy. Whisk it with an equal amount of water to dilute it back down to milk's consistency before using it in a recipe.