Buttermilk vs Milk
Buttermilk is acidic and thick; plain milk is neither. The acid is the big difference: it reacts with baking soda for lift and tenderizes the crumb. If a recipe wants buttermilk and you only have milk, sour 1 cup of milk with 1 tablespoon of lemon juice or white vinegar and let it stand 5 to 10 minutes. Straight milk leaves baked goods flatter and less tender.
At a glance
| Ingredient | Grams per cup | Type | Key trait |
|---|---|---|---|
| Buttermilk | 240 g | Dairy & Fats | Buttermilk weighs about the same as regular milk per cup. |
| Milk | 240 g | Dairy & Fats | Milk is very close to water in weight — one cup is about 240 grams. Whole, skim and low-fat all weigh within a gram or two of that. |
How to swap buttermilk and milk
- 1 tbsp lemon juice or white vinegar + milk to fill 1 cup; rest 5–15 minutes until slightly thickened (King Arthur Baking)
Full conversions: Buttermilk converter · Milk converter. More swaps: Buttermilk substitutes · Milk substitutes.
More comparisons
* Conversion figures are typical average weights for one US customary cup (236.6 ml), based on the King Arthur Baking Ingredient Weight Chart and cross-referenced with the U.S. Department of Agriculture FoodData Central database. Actual weight varies with packing, brand and humidity — see our methodology.