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Heater Wattage Calculator
Find the right heater size for your aquarium based on tank volume, room temperature and the temperature you want to hold.
Rule of thumb: about 0.12 W per litre per °C of temperature rise needed. Tropical tanks in normal rooms (20 °C room, 25 °C target) usually need 2.5–3 W per litre.
Heater Size
Temperature Rise
5.0 °C
Calculated Power
60 W
Recommended Heater
75 W
nearest standard size
Setup
1 × 75 W
single heater
For tanks over ~100 L it's safer to run two smaller heaters — if one fails you still have heating. Always size up slightly rather than down; heaters cycle on and off to hold temperature.
Related Reading
Guides that cover this topic in depth