Aquarium Heater Wattage Calculator

Calculate the correct heater size for your aquarium.

Calculate the correct heater size for your aquarium

Tank Volume (Liters)

Room Temperature (°C)

Target Temperature (°C)

Formula

Wattage = Volume × ΔT × Size Factor

How to Use

1
Enter tank volume — Input your aquarium size in gallons or liters.
2
Set room temperature — Enter the average room temperature where the tank is located.
3
Set target temperature — Choose your desired water temperature for your fish species.
4
Get heater recommendation — See the recommended wattage and whether one or two heaters are best.

A general rule is 3-5 watts per gallon. If the room temperature is much lower than the desired tank temperature, use the higher end.

For tanks over 40 gallons, using two smaller heaters provides more even heating and a safety backup if one fails.

Most tropical fish thrive at 76-80°F (24-27°C). Check your species requirements for the exact range.

An oversized heater can overshoot the target temperature if the thermostat fails. Choose one sized appropriately for your tank.

Calculate your exact tank volume.

Check appropriate stocking levels.

Plan water changes for your tank.