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Aquarium Calculators

Aquarium Heater Wattage Calculator

Heater wattage for a tank from the temperature rise needed above room temperature.

Enter values

Results update as you type.

Result

Heater wattage

300 W

Two smaller heaters are safer than one large one — if one sticks on, it cannot cook the tank on its own.

Calculated requirement
252 W
Temperature rise needed
7 °C
Watts per litre
1.667
Estimated running energy
2.117 kWh/day
Two heaters option
2 × 150 W for redundancy
Annual energy
773 kWh

About the Aquarium Heater Wattage Calculator

Heater wattage for a tank from the temperature rise needed above room temperature.

Also known as: fish tank heater size, aquarium heater calculator, watts per litre heater, tank heating.

How to use this calculator

  1. Enter tank volume, target temperature, coldest room temperature, tank location.
  2. The result updates instantly as you type — press Calculate (or Enter) at any time.
  3. Review the breakdown shown under the main result.
  4. Use Copy result or Share to save the answer or send a link with your inputs.

Formula

watts ≈ litres × (temperature rise ÷ 5) × location factor

Worked example

Using the values pre-filled in the calculator above:

  • Tank volume = 180 litres
  • Target temperature = 25 °C
  • Coldest room temperature = 18 °C
  • Tank location: Warm room, lid fitted

the calculator returns:

  • Heater wattage: 300 W
  • Calculated requirement: 252 W
  • Temperature rise needed: 7 °C
  • Watts per litre: 1.667