Baking Pan Conversion Calculator

About the Baking Pan Conversion Calculator

A recipe calls for a 9-inch round cake tin, but you only have a square one. A brownie recipe is written for an 8-inch square pan and you want to bake it in a 9 by 13. Using the wrong pan is not a disaster, but it changes the depth of the batter, and depth decides how long the bake takes and whether the middle cooks before the edges dry out.

This baking pan conversion calculator compares two pans by area. Choose the shape of each — rectangle, square or round — enter the dimensions, and it gives the scale factor to apply to the recipe so the batter stays the same depth, how much bigger or smaller the new pan is, and what to do if you decide not to scale the recipe.

How to Use the Baking Pan Conversion Calculator

Choose the shape of the recipe's pan and enter its size: length and width for a rectangle, one side for a square, the diameter for a round pan.

Do the same for your pan.

Use the same unit for both pans — inches or centimetres.

How Pan Sizes Are Compared

  rectangle area  =  length × width
  square area     =  side × side
  round area      =  π × (diameter ÷ 2)²
  scale factor    =  your pan area ÷ recipe pan area

Multiply every ingredient in the recipe by the scale factor to fill the new pan to the same depth.

Step-by-Step Example

A 9-inch round tin swapped for an 8-inch square pan.

  Round:    π × 4.5²          =  63.6 sq in
  Square:   8 × 8             =  64 sq in
  Factor:   64 ÷ 63.6         =  1.01  → use the recipe as it is

An 8-inch round recipe baked in a 9 × 13 inch pan.

  Round:    π × 4²            =  50.3 sq in
  Rectangle: 13 × 9           =  117 sq in
  Factor:   117 ÷ 50.3        =  2.33

Common Pan Sizes and Areas

A few useful equivalents follow from the table: a 9-inch round and an 8-inch square are interchangeable; two 8-inch rounds hold about the same as one 9 by 13 pan; and a 9 by 13 holds nearly twice an 8-inch square.

Changing Pans Without Scaling

Sometimes you want to keep the recipe as it is and simply use a different pan. That works, as long as you adjust the bake.

A bigger pan makes a thinner layer, which bakes faster. Start checking well before the stated time, and expect a flatter cake or thinner brownies.

A smaller pan makes a deeper layer, which takes longer. Lower the oven by about 10 °C or 25 °F so the outside does not overbake before the centre sets, and test with a skewer. Never fill a pan more than about two thirds full, or the batter may overflow as it rises.

Depth, Not Just Area

Area comparison assumes both pans are filled to the same depth. That is usually the goal, but pan height matters too. A springform or deep cake tin can hold a deeper batter than a shallow sheet pan of the same area. If a converted amount would come too close to the rim, bake the extra batter as cupcakes or a small loaf rather than risking an overflow.

Pan Materials and Colours

Dark metal pans absorb heat and brown the outside faster. Shiny aluminium reflects heat and gives paler, more even results. Glass and ceramic dishes heat slowly but hold heat well; many bakers lower the oven by about 15 °C or 25 °F when using them. Silicone gives soft sides with little browning. Changing material can matter as much as changing size.

Converting Recipes for Cupcakes

Cake batter can also be baked as cupcakes instead of a single cake. A standard cupcake holds a little under a quarter cup of batter, so a recipe for two 8-inch round layers usually makes around 24 cupcakes. Fill each paper case about two thirds full, and bake at the same temperature for roughly half to two thirds of the original time, usually 18 to 22 minutes. Test with a skewer, since cupcakes overbake quickly.

Loaf Tins and Bundt Pans

Loaf tins are deep and narrow, so they bake more slowly than a flat pan of the same volume. A standard 9 by 5 inch loaf tin holds about the same batter as an 8-inch square pan, but needs longer in the oven. Bundt and ring pans have a hole in the middle that helps heat reach the centre; compare them by volume, measured by filling the pan with water, rather than by area.

Understanding Your Result

Scale factor is the number to multiply the recipe by.

Pan areas shows the area of each pan in the unit you used.

Size difference shows how much bigger or smaller the new pan is.

What to do gives advice on scaling or adjusting the bake.

Worth knowing reminds you not to overfill the pan.

When Should You Use This Calculator?

Baking in the pan you have rather than the one in the recipe.

Turning a layer cake into a sheet cake, or the other way round.

Doubling a brownie or bar recipe.

Converting between round and square tins.

Planning bakes for a party.

Common Mistakes

Comparing pans by one side instead of area.

Using diameter as if it were radius for round pans.

Mixing inches and centimetres.

Keeping the same baking time for a much deeper batter.

Overfilling the pan.