Aquarium Calculators
Free tools for fishkeepers that show their math. Start with your tank's volume; every other number (heater wattage, gravel, running cost, dosing) depends on it.
All calculators
Volume
Aquarium volume calculator
Gallons and liters from your tank dimensions. Rectangular, cylinder and bowl tanks, glass thickness, fill level and substrate displacement.
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Heating
Aquarium heater size calculator
The heater wattage your tank needs from its volume, room temperature, target temperature and lid, plus heat-up time and running cost.
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Heating
Heater size comparison
50 W vs 100 W vs 200 W for your tank: heat-up time, thermostat duty and cost side by side, with a temperature-over-time chart.
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Electricity
Aquarium electricity cost calculator
Add up heater, filter, lights and pumps to see kWh and cost per day, month and year at your electricity rate.
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Substrate
Aquarium substrate calculator
How much gravel, sand or aquasoil to buy: pounds, liters and bags for a flat or sloped bed over your tank footprint.
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Standard tank sizes
Full sizes chart →Dimensions, real water volume, filled weight and heater size for each.
Guides
All guides →Which calculator do I need?
- Setting up a new tank? Get the real water volume with the aquarium volume calculator, then size the heater from that number.
- Buying a heater? The heater size calculator recommends a wattage from your room and target temperatures, and the heater size comparison shows whether a bigger or smaller unit is worth it.
- Choosing gravel or sand? The substrate calculator turns your tank footprint and bed depth into pounds and bags.
- Picking a tank? The aquarium sizes chart compares dimensions, real gallons and filled weight for every standard size.
- Worried about the power bill? The aquarium electricity cost calculator totals every device on the tank at your electricity rate.
Why tank volume comes first
The number on the box is a rounded, brim-full figure measured over the outside of the glass. A "55 gallon" tank with gravel, rock and the water line a little below the rim usually holds closer to 45–50 gallons of actual water. Medication doses, heater size, filter flow and stocking all depend on that real figure, so every tool here starts from it and shows the formula it uses.