For your fish tank
Eleven aquarium calculators to plan and run a healthy freshwater tank. Browse all aquarium calculators.
Tank volume calculator
True water volume in gallons and liters from your tank dimensions.
Stocking calculator
Check how full your tank is with real species data, not the inch per gallon myth.
Heater wattage calculator
Find the right heater size for your volume and temperature gap.
Water change calculator
Work out how much water to swap to hit your target nitrate level.
Filter turnover calculator
See whether your filter moves enough water for your stocking level.
Tank weight calculator
Estimate the full loaded weight and the load on your floor.
Substrate calculator
How much gravel, sand or aqua soil your tank needs, in pounds and liters.
Glass thickness calculator
Check the glass thickness and safety factor for your tank.
Salt mix calculator
How much marine salt to reach a target salinity for brackish or saltwater.
Light calculator
Lumens and LED wattage for low, medium or high light plants.
Setup cost calculator
Add up the one time cost of starting a tank, with cost per gallon.
For your dog
Four dog calculators for feeding, growth and age. Browse all dog calculators.
Dog food calculator
Daily calories and cups from your dog weight and activity.
Raw dog food calculator
Daily raw food as a percent of weight, with the 80/10/10 split.
Puppy weight calculator
Estimate your puppy full grown adult weight by breed size.
Dog age calculator
Convert your dog age into human years by breed size.
One place for two kinds of pet
The name says it: Tank and Tail is for the tank and the tail. On the aquarium side, the tools turn the common questions of fishkeeping into clear answers, from the true water volume of a tank to safe stocking, heater size and water changes. On the dog side, they help with the everyday numbers of dog care, like how much to feed, how big a puppy will grow, and how old a dog is in human years.
Every tool runs in your browser, shows its working, and is built to be quick on a phone. You never need an account, and nothing you type is stored.
Estimates for planning, not professional advice
Each result is a well tested estimate for planning. Living tanks vary with plants, feeding and flow, and every dog is different in breed, age and health, so treat the numbers as a strong starting point rather than the last word. For a sick fish, an aquatic vet is the right call, and for feeding or health questions about your dog, ask your own vet.
Used that way, the calculators do the math while you and your vet make the decisions, which keeps your pets healthy and your planning simple.
Frequently asked questions
What is Tank and Tail?
Tank and Tail is a free collection of calculators for two kinds of pet: the tank and the tail. It helps you plan a healthy aquarium and care for your dog, from tank volume and stocking to dog food and puppy weight.
Are the tools free to use?
Yes. Every tool is free, needs no account, and runs in your browser. Nothing you enter is stored.
Do you cover both fish and dogs?
Yes. The aquarium calculators cover freshwater fishkeeping, and the dog calculators cover feeding, puppy growth and dog age. More may be added over time.
Do the tools work on a phone?
Yes. The whole site is mobile first and works down to a 360 pixel wide screen, so you can use it at the fish store or the vet.
Do I need to sign up or install anything?
No. There is no sign up, app or plugin. Open the site in any modern browser and start.