Buttermilk Substitute: 3 Ways to Make It at Home
No buttermilk? Make a cup from milk and lemon juice or vinegar in 5 minutes, or use yogurt thinned with milk. Exact ratios for baking and frying.
By The UnitFig Editorial Team · August 29, 2026 · reviewed against NIST and SI reference sources
The 5-minute acid method
Add 1 tablespoon (15 ml) lemon juice or white vinegar to a measuring cup, then fill to 1 cup (240 ml) with milk. Stir and rest 5–10 minutes until it curdles slightly. This is the closest match for pancakes, biscuits, and cakes.
Other reliable swaps
Plain yogurt: use 3/4 cup (180 g) yogurt + 1/4 cup (60 ml) milk to make 1 cup buttermilk. Thinner and tangier.
Sour cream: 3/4 cup (180 g) sour cream + 1/4 cup (60 ml) milk. Rich, good for savory frying batters.
Powdered buttermilk: follow package; typically 1 tbsp powder + 1 cup water.
Why the acid matters
Buttermilk’s acidity reacts with baking soda to create lift. A sweetened non-dairy milk without acid will not trigger the same rise — always include the lemon or vinegar step.
Frequently Asked Questions
Can I use water instead of milk?
Not for taste or richness — use milk (dairy or unsweetened plant milk) so the substitute still adds body and flavor.
Does it work with almond milk?
Yes, unsweetened almond or soy milk plus lemon juice curdles and works the same way for vegan baking.
Quick Summary
The easiest buttermilk substitute is 1 cup milk + 1 tablespoon acid, rested 10 minutes. Yogurt or sour cream thinned with milk also work. Keep the acid in the mix so baking soda still reacts.
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Disclaimer
Unit conversions on this site use internationally recognized, fixed conversion factors (for example, 1 inch = 2.54 cm, 1 pound = 0.45359237 kg, 1 °F = (°C × 9/5) + 32). They are provided for general, informational, and educational use. For applications where accuracy is critical — such as medical dosing, engineering, scientific research, trade, or legal compliance — always verify results against authoritative sources such as the U.S. National Institute of Standards and Technology (NIST) and the official International System of Units (SI) brochure, and follow any applicable local standards.
Exact Constants & Authoritative Sources
Every conversion on this page uses the fixed, internationally agreed constants below — drawn from NIST and the SI Brochure. No values are estimated or rounded as if exact. See the full list on our Sources & Standards page.
- EXACT1 US gallon (gal) = 3.785411784 litres (exact, 231 in³)
- EXACT1 US fluid ounce (fl oz) = 29.5735295625 mL (exact, 1/128 gal)
- EXACT1 US cup = 236.5882365 mL (exact, 8 fl oz)
- EXACT1 US pint (pt) = 473.176473 mL (exact, 16 fl oz)
- EXACT1 US quart (qt) = 946.352946 mL (exact, 32 fl oz)
- EXACT1 litre (L) = 1000 millilitres (definition)
Common Pitfalls & How to Avoid Them
US vs. Imperial (UK) cups
A US cup is 236.59 mL, but a UK/metric cup is 250 mL and an Imperial cup is ~284 mL. Recipes from different countries are not interchangeable drop-in.
Fluid ounce is volume, not mass
A US fl oz is 29.57 mL of volume. 1 fl oz of water ≈ 29.57 g, but 1 fl oz of honey or oil weighs more. Do not treat fluid ounces as grams.
Teaspoon/tablespoon sizes differ
1 US tbsp = 14.7868 mL; 1 US tsp = 4.92892 mL. Metric measuring spoons are 15 mL and 5 mL — close but not exact; for baking precision use weighed grams.
A unit-conversion reference site has no manufacturer-specific or device calibration parameters, so "layered tuning" does not apply here. The only real error-handling is input validation: the converter rejects non-numeric, empty, or out-of-range entries and shows a clear message, then falls back to exact constants above. No estimated or rounded figures are ever presented as exact.
Authoritative sources for this page
- NIST (U.S. National Institute of Standards and Technology) — NIST SP 330 — The International System of Units (SI), 2019 edition
- BIPM (International Bureau of Weights and Measures) — SI Brochure — The International System of Units (9th edition)
Last Updated 2026 | This article was reviewed for accuracy