How to halve a recipe
The quantities are easy. The egg and the tin are not.
Divide everything by two. The two real problems are the egg (beat one and weigh 25 g) and the tin, which needs half the area or the batter will be too shallow.
Awkward half measures
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| Original amount | Half | How to measure it |
|---|---|---|
| 1 cup | 1/2 cup | Straightforward |
| 3/4 cup | 6 tablespoons | 3/8 cup does not exist: use spoons |
| 1/3 cup | 2 tbsp + 2 tsp | A sixth of a cup |
| 1/4 cup | 2 tablespoons | Straightforward |
| 1 tablespoon | 1 1/2 teaspoons | 3 teaspoons make a tablespoon |
| 1 large egg | 25 g beaten egg | Beat one whole and weigh half |
| 1 packet of yeast (7 g) | 3.5 g | A little over one teaspoon |
The egg
It is the one ingredient that cannot be split. The fix is always the same: beat a whole egg with a fork until yolk and white are combined, then weigh half. A large egg without its shell is about 50 g, so half is 25 g.
The rest brushes a pie or makes a small omelette, so nothing is wasted.
The tin: half the area, not half the diameter
This is the classic mistake. Halve a recipe from a 9 in tin and use a 4.5 in one and you will be badly short: the area does not halve, it quarters.
Half the area of a 9 in tin (63.6 sq in) is 31.8 sq in, which is a 6.4 in tin. Quick rule: divide the diameter by 1.41 for half the area.
Baking time drops, but not by half
With a properly reduced tin, the batter depth is similar and so is the time. Even so, start checking 5-10 minutes early: domestic ovens heat unevenly and a smaller bake feels it sooner.
What not to reduce
- The cooking liquid in a stew, if the pot stays the same size: proportionally more would evaporate and it would catch.
- Salt can stay a touch above half: when quantities shrink, perceived saltiness drops less than expected.
Sources and methodology
The half-measure equivalences are cup and spoon arithmetic. The tin area calculation is geometry: the area of a circle grows with the square of the radius.
Frequently asked questions
How do I halve an egg?
Beat a whole egg and weigh 25 g, roughly half a large egg without the shell. The rest is useful for glazing or another recipe.
What is half of 3/4 cup?
6 tablespoons, since a cup is 16 tablespoons. Three eighths of a cup is not a real measure.
What tin should I use for a halved recipe?
One with half the area, not half the diameter. Divide the diameter by 1.41: a 9 in tin becomes about 6.4 in.
Do I need to cut the baking time?
With the right tin, only slightly: start checking 5-10 minutes early. In the original large tin the batter is shallower and will bake considerably faster.