How many brownies from a 9x13 tin? Portions for every common tin

A 9 × 13 inch tin gives 24 brownies cut 4 by 6, each about 57 × 55 mm. Cut it 3 by 4 for 12 large ones (about 76 × 83 mm), or 4 by 8 for 32 small ones (about 57 × 41 mm).

The count is the easy half. The part that catches people out is the portion size: whether the tin cuts cleanly into the size you sell, or leaves a strip of offcut down one side every time.

The brownie cutting calculator does this for any tin and any count, and prints a cutting guide at actual size.

Portions by tin

Cut evenly, so every portion is the same size and nothing is left over. The first number is the arrangement; the size is each portion, in millimetres.

Tin	9	12	16	24	32
8 × 8 in (20 × 20 cm)	3 × 3, 68 × 68	3 × 4, 68 × 51	4 × 4, 51 × 51	4 × 6, 51 × 34	4 × 8, 51 × 25
9 × 9 in	3 × 3, 76 × 76	3 × 4, 76 × 57	4 × 4, 57 × 57	4 × 6, 57 × 38	4 × 8, 57 × 29
20 × 30 cm	3 × 3, 67 × 100	3 × 4, 67 × 75	4 × 4, 50 × 75	4 × 6, 50 × 50	4 × 8, 50 × 38
9 × 13 in (23 × 33 cm)	3 × 3, 76 × 110	3 × 4, 76 × 83	4 × 4, 57 × 83	4 × 6, 57 × 55	4 × 8, 57 × 41

Some counts are better than others in a given tin. Sixteen from an 8 × 8 is a perfect square; sixteen from a 9 × 13 is a long finger. Twenty-four from a 20 × 30 cm tin is a perfect 5 cm square; twenty-four from an 8 × 8 is a thin bar. When a count gives you long, thin portions, the next count up or down usually gives you a better shape.

When the portion size is fixed

If you sell by size — because the price, the box or the café's plate was set against it — the question turns round: how many of that size does the tin hold?

Tin	2 inch squares	5 cm squares	3 inch squares
8 × 8 in	16, no offcut	16, 3 mm spare	4, big offcut
9 × 9 in	16, 2.5 cm offcut	16, 3 cm offcut	9, no offcut
20 × 30 cm	15, big offcut	24, no offcut	6, big offcut
9 × 13 in	24, 2.5 cm offcut	24, 3 cm offcut	12, 2.5 cm offcut

Look at the 20 × 30 cm tin. Cut into 5 cm squares, it gives 24 with nothing spare. Cut into 2 inch squares — less than a millimetre bigger each way — the fourth square across no longer fits, and the count drops to 15. A portion size that is a tidy number in the wrong unit can cost you a third of the tray.

That is the case for choosing the tin and the portion size together. If you sell 2 inch brownies, an 8 × 8 inch tin cuts them perfectly. If you sell 5 cm ones, a 20 × 30 cm tin does.

Measure across the top

Brownie tins usually have sloped sides, so the base is smaller than the top. A tin sold as 9 × 13 can measure a centimetre less across the bottom. The brownie is the size of the top of the tin where it rose to, so measure there — or measure the baked slab after you turn it out, which is the most accurate of all.

Moving a recipe to a different tin

Scale by area, not by side length. A 9 × 13 inch tin is not "a bit bigger" than an 8 × 8 inch one: it holds nearly twice as much.

From	To	Multiply the recipe by
8 × 8 in	9 × 9 in	1.25
8 × 8 in	9 × 13 in	1.8
20 × 20 cm	20 × 30 cm	1.5
20 × 30 cm	23 × 33 cm	1.25

Scaled like that, the batter comes to the same depth, so the baking time is roughly the same. Start checking a few minutes early all the same — a bigger tin holds its heat differently in the middle.

Quick answers

How many brownies from an 8x8 tin? Sixteen 2 inch squares, or nine larger ones about 68 mm square.

How many brownies from a 9x13 tin? Twenty-four standard, twelve large or thirty-two small.

How many brownies from a 20 x 30 cm tin? Twenty-four 5 cm squares, with nothing left over.