Wedding cakes are generally custom-ordered in various shapes and sizes. The size of the cake usually depends on the number of guests attending the wedding. Each serving of wedding cake should measure 1 inch across, 2 inches deep and 4 inches tall, according to Wilton, the renowned cake supply company. Most bakeries will calculate the number of servings you need when you order the cake. However, you can calculate the amount of cake you need by consulting a serving chart or by completing a mathematical formula.

Visit EarlenesCakes.com and consult the serving chart provided to determine the number of wedding cake servings that apply to your cake. Find the pan size in the left column and match it to the appropriate circumference. When you have found your cake's size, read the number highlighted in yellow directly to the right of the pan size and circumference; that is the number of servings your cake will yield.

Use the online serving calculator provided at ShinyMetalObjects.com if you cannot find the number on a premade serving chart. Enter the width, length and height of your cake in the calculator and click "Continue." Choose the cake's dimensions on the next screen by checking the appropriate box with your mouse. Click "Calculate." The calculator will supply the appropriate number of servings that match the size of your cake.

Write down the width, length and height of your square or rectangular cake if you are unable to find the number easily on a serving chart or by using the serving calculator. Use a handheld or computer-based calculator and enter the width. Multiply the width by the length of your cake. Multiply that total by the height of your cake. The number you get will be the cubic inches of your cake. Divide that number by 8, since each serving will total 8 cubic inches, and the final number will reflect the number of servings your cake will yield. For example, a 9-inch-by-13-inch cake that is 4 inches tall requires you to multiply 9 by 13. Then multiply the total, which is 117, by 4. The result is 468. Divide 468 by 8 on your calculator and it will display 58.5. This means your cake will provide 58 guests with an appropriate portion.

Write down the diameter and height of your round cake. Using your calculator, enter the radius of your cake. The radius is half the diameter. Multiply the radius times the radius. For example, if you are baking with a 14-inch round pan, multiply 7 by 7. Multiply the answer by pi. Round pi to 3.14. Multiply that result by the height of your cake. Finally, divide that number by 8 to determine the number of servings your cake will yield. For example, a 14-inch round pan that bakes a 4-inch-tall cake requires you to first multiply 7 by 7. The answer, 49, must be multiplied by 3.14. Press the "Equals" symbol on your calculator and it will display the number 153.86. Multiply that total by 4 and your calculator will display the number 615.44. To determine the number of guests your cake will serve, divide that number by 8. A cake that size will serve 76 people.