Kleiber's Law

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Kleiber's law

named after Max Kleiber's biological work in the early 1930s, is the observation that, for the vast majority of animals, an animal's metabolic rate scales to the ¾ power of the animal's mass. Symbolically: if q0 is the animal's metabolic rate, and M the animal's mass, then Kleiber's law states that <math>q_0 \sim M^{¾}</math>. Thus a cat, having a mass 100 times that of a mouse, will have a metabolism roughly 32 times greater than that of a mouse. In plants, the exponent is close to 1.

Max Kleiber

was born and educated in Zürich, Switzerland. He graduated from the Federal Institute of Technology as an Agricultural Chemist in 1920, earned the ScD degree in 1924, and became a private dozent after publishing his thesis The Energy Concept in the Science of Nutrition.

He came to the Animal Husbandry Department of UC Davis in 1929 to construct respiration chambers and conduct research on energy metabolism in animals. Among his many important achievements, two are especially noteworthy. In 1932 he came to the conclusion that the ¾ power of body weight was the most reliable basis for predicting the basal metabolic rate (BMR) of animals and for comparing nutrient requirements among animals of different size. He also provided the basis for the conclusion that total efficiency of energy utilization is independent of body size. These concepts and several others fundamental for understanding energy metabolism are discussed in Kleiber's book, The Fire of Life published in 1961 and subsequently translated into German, Polish, Spanish, and Japanese.


  1. Max Kleiber (1932). "Body size and metabolism". Hilgardia. 6: 315–351. doi:10.3733/hilg.v06n11p315.
  2. Jump up ^ Kleiber M (1947). "Body size and metabolic rate". Physiological Reviews. 27 (4): 511–541. PMID 20267758.
  3. West, Geoffrey; Brown, James H.; Enquist, Brian J. (1997). "A General Model for the Origin of Allometric Scaling Laws in Biology". Science. 276 (5309): 122–6. doi:10.1126/science.276.5309.122. PMID 9082983.