The ratio, properly explained

Oil to Butter Ratio

The practical oil-to-butter multiplier is 1.25 because butter is about 80% fat. The commonly copied 1.333 figure comes from inverting 0.75 rather than balancing fat.

Oil to butter converter

Use

1¼ cups

Which is also

284 g
20¼ tbsp
2½ sticks

Quick rule: easy to remember and fine for most bakes. Switch to Exact for a fat-matched result.
About 80% fat, 16-17% water and milk solids. The water is why butter and oil are not a straight swap.

Show the maths

Formula	240 ml × 1.25 = 300 ml
Source	218 g · 218 g fat
Result	283.75 g · 227 g fat
Ratio	×1.3016

Oil to butter: multiply by 1.25. Butter to oil: use 0.80 for a reversible fat match or 0.75 as the familiar shortcut.

Common amounts

Oil to butter ratio chart

Source	Quick	Exact	Exact grams
⅛ cup	⅛ cup	⅛ cup	34.06 g
¼ cup	⅓ cup	⅓ cup	68.13 g
⅓ cup	⅜ cup	⅜ cup	90.83 g
½ cup	⅝ cup	⅝ cup	136.25 g
⅔ cup	⅞ cup	¾ cup	181.67 g
¾ cup	0.94 cups	⅞ cup	204.38 g
1 cup	1¼ cups	1¼ cups	272.5 g
1½ cups	1⅞ cups	1¾ cups	408.75 g
2 cups	2½ cups	2⅜ cups	545 g

What matters in the kitchen

How to use this conversion

Oil to butter

1 ÷ 0.80 = 1.25, based directly on butter's approximate fat content.

Butter to oil

100 g butter carries about 80 g fat, so 80 g oil is the exact reverse by weight.

Why not 1.333

That number is 1 ÷ 0.75, an inversion of a rounded shortcut rather than a composition-based formula.

Questions about this tool

Oil to Butter Ratio FAQ

What is the key result from the Oil to Butter Ratio?