About AquaCalcs

AquaCalcs is a collection of sixteen free calculators for freshwater and planted-tank keepers, covering the maths that comes up again and again in the hobby: tank volume, stocking, heater wattage, filter turnover, water changes, CO₂, substrate, glass thickness, running costs and more.

Why we built it

Most aquarium calculators online are black boxes. You type a number, you get a number, and you have no way to know whether the answer is based on physics, on a fifty-year-old rule of thumb, or on nothing at all. When we started planning our own tanks, that opacity bothered us enough to do something about it.

So every AquaCalcs tool follows three rules:

• The formula is on the page. Every calculator shows the equation it uses and where the equation comes from — whether that is straightforward geometry, standard water chemistry, or an industry sizing convention.
• The limitations are on the page too. Rules of thumb break down; where they do, we say so. The stocking calculator spends as many words on why the cm-per-litre rule fails as on the rule itself, because that is what makes the number useful.
• Everything runs in your browser. No accounts, no uploads — nothing you type into a calculator is sent to our servers.

What AquaCalcs is not

These tools produce planning estimates for a hobby, not professional advice. The glass thickness and tank weight pages in particular are references to help you ask better questions — they are not a substitute for a professional tank builder or structural engineer, and nothing here is veterinary advice. Where a decision affects the safety of your home or the health of your animals, please involve a qualified professional.

Corrections welcome

If you find an error — in a formula, an assumption, or a word — we genuinely want to hear about it. Tell us via the contact page and we will check it and fix it. The site gets better mainly through reader feedback.