Walnuts, including the shell and kernel, weigh 11 to 23.6 grams, depending on the variety grown. Walnut kernels, which often make up over half of the nut's volume, weigh from 5.5 to 14.8 grams. Whole walnuts measure 30.8 to 34.6 millimeters in width and 37 to 43.6 millimeters in length.
Factors such as variety, soil conditions, pruning, weather conditions, and disease and insect resistance also affect the finished size of a walnut crop. Walnuts grown in the United States adhere to USDA standards regarding shelled walnuts. Walnuts are sold in a variety of sizes, including halves, pieces, topping pieces and walnut meal.