The Hass Avocado Board states that one-fifth of an avocado weighing in at 1 ounce or 30 grams contains 50 calories. One whole medium-sized avocado without its seed or its skin that weighs 5 ounces or 150 grams is 250 calories.

The Hass Avocado Board explains how to discover the number of calories contained in an avocado. First, weigh the avocado in grams, then divide the number of grams by 30. Finally, multiply the quotient by 50. For example, if half a cup of cubed avocado weighs 75 grams, divide 75 by 30, which equals 2.5. Multiply 2.5 by 50, which equals 125. A half cup of cubed avocado that weighs 75 grams has 125 calories.