1/3 Cup of Oil Equals How Much Butter? | The Simple Ratio

Use about 1/3 cup plus 2 tablespoons of butter (roughly 7 tablespoons) to replace 1/3 cup of oil.

You’re halfway through measuring ingredients for banana bread when you realize the recipe calls for 1/3 cup of oil and you’re fresh out. There’s butter in the fridge, but substituting it without knowing the right ratio can leave you with a greasy mess or a dry crumb.

The honest answer requires a small adjustment. Oil is 100% fat, while butter contains about 80% fat and 20% water. To match the fat content of your original ingredient, you need to use about 25% more butter by volume. Here is exactly how that math works for 1/3 cup of oil, plus what to expect from the swap.

The Simple Conversion for 1/3 Cup of Oil

The standard substitution ratio for oil to butter is 3:4. For every 3 parts of oil, you need 4 parts of butter. This accounts for the water content in butter that doesn’t contribute to the fat structure of your bake.

For 1/3 cup of oil, the equivalent amount of butter is approximately 1/3 cup plus 2 tablespoons (about 7 tablespoons). King Arthur Baking explains that butter contains around 18% water and at least 80% butterfat, so using more butter by volume is necessary to deliver the same amount of pure fat.

If you prefer weighing your ingredients for accuracy — and King Arthur Baking recommends this for consistent results — 1/3 cup of oil weighs roughly about 75 grams. The butter equivalent sits closer to 90 grams, though exact numbers vary slightly by brand and temperature.

Why the Swap Changes Your Texture

The math is straightforward, but how the swap actually behaves in your mixing bowl depends on what you are making. The water in butter serves a structural purpose, and oil plays by different rules entirely.

• Moisture and steam: The 20% water in butter turns to steam in the oven, helping lift batters and create a light crumb. Oil releases no steam, so oil-based cakes are often denser and more moist.
• Creaming ability: Cookies and layer cakes rely on creaming solid butter with sugar to trap air. Oil cannot be creamed, so substituting it will produce a flatter, chewier texture.
• Flavor impact: Butter adds a rich, creamy flavor that is hard to replicate. Oil is neutral unless you use a flavorful one like olive or coconut, which carries its own character.
• Shelf life: Oil-based baked goods tend to stay moist longer than butter-based ones because there is no water to evaporate over time.
• Sautéing and frying: Butter burns easily because its milk solids scorch at high heat. Oil has a much higher smoke point, making it the better choice for searing or frying.

These trade-offs don’t mean one fat is better than the other — they mean you should choose based on the result you want. Understanding them helps you swap with confidence rather than guesswork.

Handy Conversion Chart for Common Amounts

Once you know the pattern, the rest of the conversions fall into place. The table below covers the most common measurements you will encounter in recipes calling for oil.

If you don’t want to do the math yourself, Omnicalculator’s oil to butter ratio calculator handles any amount instantly and adjusts for both volume and weight.

How to Substitute Butter for Oil in a Recipe

Working in reverse — replacing butter with oil — is equally common and uses the same ratio in the other direction. You simply reduce the amount of fat by volume to account for the missing water.

1. Calculate the new amount: Multiply the butter volume by 0.75 (or 3/4). For 1/2 cup of butter, you would use about 1/3 cup of oil.
2. Melt the butter first: Oil is a liquid at room temperature, so solid butter won’t incorporate the same way. Melt it gently and let it cool slightly before adding it to the batter.
3. Account for the missing water: Since oil doesn’t have the 20% water that butter does, the batter may be thicker. Adding a splash of milk or water — about 1 to 2 tablespoons per cup of butter replaced — can help restore the moisture balance.
4. Watch the salt: If you are using salted butter in place of oil, reduce the added salt in the recipe slightly to avoid an overly salty result.
5. Check doneness early: Oil-based batters can brown differently than butter-based ones. Start checking for doneness a few minutes before the recipe’s suggested time.

Quick breads, muffins, and pancakes handle this swap especially well. Cookie recipes are the trickiest because the creaming step is so important to their structure.

The Best Fats for Different Baking Tasks

Knowing the best times to reach for butter versus oil can make your baking more successful from the start. Instacart’s conversion guide notes 1/3 cup of oil, which perfectly illustrates the reverse ratio for quick reference.

For quick breads and muffins where you want a tender crumb and lasting moisture, oil is an excellent choice. For anything that depends on volume, lift, or flaky layers, butter is usually the better call.

The Bottom Line

Converting 1/3 cup of oil to butter requires using about 7 tablespoons, or 1/3 cup plus 2 tablespoons, based on the 3:4 oil-to-butter ratio. The swap works wonderfully in quick breads and muffins, but expect a denser, more tender crumb compared to the original butter version.

Every kitchen scientist has a preference, and neither fat is universally better — a heavy hand with oil in a delicate genoise or a butter swap in a recipe built for neutral flavor might need a second look. For the vast majority of cakes, pancakes, and brownies, this ratio will steer you right.