Aquarium Heater Size Calculator
Heater wattage depends on both your tank size and how far you need to heat above room temperature. Enter both for a recommendation.
Frequently Asked Questions
How many watts per gallon for an aquarium heater?
The standard guideline is about 3–5 watts per gallon. Use the lower end if your room stays warm and the higher end (or more) if the room is cold or the tank is large.
Should I use one heater or two?
For tanks over about 40 gallons, two smaller heaters at opposite ends give more even heating and a safety margin — if one sticks off you have backup, and if one sticks on it's less likely to cook the tank.