Aquarium calculators for planning a healthy tank
Six simple tools that do the math for freshwater aquariums, so you can plan a tank that stays stable. Enter your numbers and get gallons, watts, turnover and weight in seconds.
Pick a calculator
Tank volume calculator
True water volume in gallons and liters from your tank dimensions.
Stocking calculator
Check how full your tank is using 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.
What this site does
Tank and Tail turns the common questions of fishkeeping into quick answers. Instead of guessing, you get numbers you can plan around: the real volume of water after substrate and the rim gap, a stocking estimate built from adult size and bioload rather than the old inch per gallon rule, and a heater size matched to how far you need to raise the temperature.
Every result is an estimate for planning. Living tanks vary with plants, feeding, flow and the age of your fish, so treat these tools as a strong starting point and keep testing your water. All calculations run in your browser, nothing is stored, and you never need an account.