What this site is for
Fishkeeping runs on numbers. How much water does the tank really hold? How big a heater? How many fish? Most answers online are either a rough rule of thumb or a calculator that gives a figure with no explanation.
FinsAndFigures does it differently. Each calculator here:
- shows its working: the formula, a worked example and the source of every rule of thumb are on the page;
- gives both unit systems: US gallons and inches beside litres and centimetres, so a guide written in one country works in another;
- explains the answer in plain words and tells you what to do with it next;
- is free, with no sign-up, and works on a phone at the side of the tank.
How the calculators are made
Every formula lives in one shared calculation library and is tested against published worked examples and manufacturers' figures before it goes live. When we change a formula, the tests run again. The method behind each tool is set out on our How we calculate page.
The species data behind the stocking calculator (adult size, minimum tank, group size, temperature and pH) follows the mainstream care consensus from established references such as Seriously Fish and FishBase. Where sources disagree, we take the more cautious figure.
Independent
FinsAndFigures is an independent website. It is not owned by, or tied to, any aquarium manufacturer or shop. No brand can pay to change a calculation or a recommendation. How the site earns money is explained in our editorial and affiliate policy.
Tell us when we are wrong
Calculators are only useful if they are right. If a result looks wrong, a species is missing, or a page is unclear, write to hello@finsandfigures.com. Corrections are checked and published quickly.