Mass and size calculator: if you became an animal

How it works

SizeCurculator

Compares the linear dimensions of a person or pet with those of any animal. Not "roughly like a cat", but an exact ratio.

Three types of dimension are compared: length — body length, height — height at the shoulder or standing height, circ — circumference. Circumference does not stand in for length or height. If one organism has a length and the other a height, comparison is still possible: the tool shows that different types are being compared and notes this.

The target dimension is entered in millimetres or taken from the pet profile. For the model animal the life stage and sex are chosen, where data differ by sex. By default the adult stage is used — or the stage closest to the target organism's age, if the age is known.

The result is the model's dimension, the "target is larger than model" ratio and its inverse. Units adjust to the magnitude: millimetres, centimetres or metres.

MassCurculator

Compares the mass of a person or pet with the mass of any animal. The target mass is entered manually or taken from the profile.

Mass depends heavily on age. The stage and sex are chosen for the model. If the target organism's age is known, the stage is selected using the same age-conversion logic as in AgeCurculator: the equivalent age is translated into the model's age, and the nearest stage is taken from that.

Within a stage, mass is not a point but an interval. For taxa and breeds (not for a specific pet) the calculator shows the interval and lets you pin a point inside it. If both mass and body size are available, refining the size extrapolates the mass: a larger individual is predictably heavier.

The result is the model's mass and two ratios. Units are grams or kilograms.

We know that an animal's exact birth date is often unknown. That's why the birth-date picker lets you set an approximate range of dates or ages. The finest precision of that range is 15 minutes. We also take time zones into account to work out the birth date as accurately as possible.

How others compare: popular ways to match your weight and size to an animal

Imagine an evil wizard turned you into a toad, or a genie turned you into a lion. What would you be like? MassCurculator takes this question seriously: it accounts for your age, weight and height and picks an animal at the same stage of life, with the size and mass that match that age. Here is how people usually compare humans and animals by weight and size, and why that is not enough.

"How many cats do I weigh": simple division

The most popular method is to divide your weight by the animal's: a 70 kg person "weighs" as much as 17 Maine Coons of 4 kg, or one and a half Great Danes. It is vivid, but it answers "how many", not "what would I be". Plain division ignores whether the animal is an adult or a youngster, and it ignores sex, although males and females of many species differ a lot in weight.

Scaling up: the square-cube law and allometry

The second method simply scales an animal up to human height: an ant as tall as a person, a mouse the size of a dog. Galileo already noticed, and J. B. S. Haldane explained in his essay "On Being the Right Size" (1926), that this does not work: double the length and mass grows about eightfold, while bone and muscle cross-sections grow only fourfold. Biologists describe real proportions with power laws, called allometry (Julian Huxley, 1932): large species have relatively thicker bones, small ones thinner. A mouse stretched to human height would not look like a real mouse.

Why a single number is inaccurate

An animal's mass and size are tightly tied to its life cycle. A two-month-old Great Dane puppy weighs about as much as an adult Toy Poodle and reaches 50–80 kg by two years; a Maine Coon kitten keeps growing until 3–4 years, while a Siamese cat stops at about one year. A tadpole and an adult frog have entirely different bodies. Compare an adult human with an "average" animal, and a child and an elderly person get the same animal, although they should turn into a youngster or an old animal.

How MassCurculator converts

That is why AgeCurculator is built into the transformation calculator. First your age is converted to the age of the chosen animal using life-cycle control points; then the life stage and sex of the model are chosen, and the mass and size norms of that stage are used. Your position within the human norm is carried over to the same position within the animal's norm: a person large for their age becomes a wolf large for its age, not an average one. It works both ways, so you can also see what kind of person your pet would be.

Man and woman: height and weight in the other sex

The same norms differ between men and women: on average men are taller and heavier, and women stop growing earlier. So MassCurculator can convert weight and height not only between a human and an animal but also between a woman and a man, just as AgeCurculator converts a man's age into women's years and back, taking age into account rather than a flat "plus 10 centimetres".

The future of MassCurculator: mass, size and the life cycle

Mass and size are not fixed numbers but a curve that follows the life cycle: fast growth of the young, an adult plateau and, in many species, weight loss in old age. Next we want to describe this curve more precisely by breed and sex, add more species with measured growth stages, and account for how diet, keeping conditions and diseases affect weight and size. We collect data from veterinary and zoological scientific papers and databases, as well as user data. If you want to help, keep a pet diary on Zveriki: weight and size by age make the forecasts better. More on age is on the AgeCurculator hub.