The normal spleen size in adults is measured by its maximum length from upper to lower pole, which should not exceed 13 cm. A thickness of 6 cm is also a useful cutoff. Size and weight vary between individuals. Splenomegaly is defined as a spleen weighing over 400g or with dimensions exceeding the normal range. Splenic size in children is measured by the long axis, with percentiles provided for different age groups from 0 months to 15 years.