Cake Pan Size Converter

This is the part that trips people up, and it is worth thirty seconds of thought because it changes the answer.

Suppose a recipe fills an 8-inch round tin two inches deep and you want to use a 9-inch round of the same depth. By volume the pans differ by 27%, and by area they also differ by 27%, so either answer works. The two only agree because the pans are the same depth.

Now suppose your 9-inch tin is three inches deep. By volume it holds 90% more, so scaling by volume means nearly doubling the recipe — and you would get a cake half as tall again as the original, baking far more slowly in the middle. By area it still needs only 27% more, and the batter sits at the original two inches. The second answer is the one you want.

The rule of thumb: scale by area to keep the cake the same, scale by volume to fill the pan. For cakes, brownies and traybakes you almost always want the first.

Bake time. Even at the same batter depth, a wider pan has more edge relative to its middle and tends to finish sooner. Start checking about 20% earlier than the recipe says, and go by a skewer rather than by the clock.

Oven temperature. If the batter ends up noticeably deeper than the original, dropping the oven by 15 to 25 °F and baking longer helps the middle set before the outside dries. If it ends up shallower, leave the temperature alone and just check sooner.

How full to fill. Cake batter is usually filled to between half and two thirds of the pan height so it has room to rise. If a conversion asks you to fill a pan much fuller than that, split it across two pans instead.

Structure. Scaling a delicate sponge a long way changes how it holds together, and a very thin layer in a very wide pan can dry out before it colours. Big jumps are better done as two batches than as one large one.

Measure across the inside of the rim, not the outside, and measure the depth on the inside too. On a tapered tin, measure the base rather than the top, since the base is what the batter sits on.

Bundt and tube pans are the awkward case. They are fluted and sloped, so the cylinder their outside dimensions describe holds more than the pan does. The capacity figure this page gives for them is an upper bound. The reliable method is to fill the pan with water a cup at a time and count; that number is worth writing on a label taped to the tin.

Every figure below comes from the calculator, using base area.

That last row is the one people get wrong most often. Two 6-inch tins have more base area between them than a single 8-inch tin, so a two-layer recipe baked as one 8-inch cake needs scaling down, not up.

Once you have the multiplier, the recipe scaler applies it to a whole ingredient list and returns kitchen fractions rather than decimals, flagging the ingredients that resist straight multiplication — leavening, salt, strong spices and eggs.

For bread rather than cake, where everything is expressed against flour weight instead of against a pan, the baker’s percentage calculator is the right tool.