# Guide to the animal calculators

The animal calculators are for pet owners. Two estimate a dog's or a cat's age in human years, one works out the water volume of an aquarium, and one estimates how much cat litter you need.

## Animal

### [Aquarium Volume Calculator](https://www.calculator.land/calculators/aquarium-volume/)

Works out the water volume of a rectangular, cylindrical, bow-front or hexagonal tank from measurements in inches or centimetres. It gives the volume in US gallons, litres and UK gallons, and a chart sets the gross volume beside an estimated net volume that allows about 15% for substrate and decor.

### [Cat Age Calculator](https://www.calculator.land/calculators/cat-age/)

Estimates a cat's age in human years with the 15-9-4 rule: 15 years for the first year, 9 for the second and 4 for each year after that. It names the life stage and marks the cat on an age curve, and a separate section lists the physical signs vets look for in each age range when the birthday is unknown.

### [Cat Litter Calculator](https://www.calculator.land/calculators/cat-litter/)

Estimates how much cat litter you need from the number of cats and litter boxes, the box size, the litter depth and the type of litter (clumping or non-clumping clay, silica gel or natural). It gives the total for the first month (initial fill plus top-ups) and the ongoing monthly amount in pounds and kilograms with a bar chart of the two, and shows the number of boxes by the N+1 rule (one more box than cats).

### [Dog Age Calculator](https://www.calculator.land/calculators/dog-age/)

Estimates your dog's age in human years with the UCSD formula, which is based on DNA methylation, from a birth date or an age in years and months, adjusted for four size categories. It shows the life stage, the age at which a dog of that size counts as a senior, the typical lifespan and a life timeline chart, and can add the result by the older AVMA rule for comparison.