Aquarium Heater Size Calculator
By Tank Volume
Calculate heater wattage from tank volume
gallons
°F
°F
By Tank Dimensions
Calculate from tank dimensions in inches
inches
inches
inches
°F
°F
Formula
Watts Needed ≈ Tank Volume (gallons) x Temperature Difference (°F) x 0.5
Frequently Asked Questions
How many watts per gallon do I need for an aquarium heater?
A general guideline is 3-5 watts per gallon for a 10°F temperature difference. If the room is much cooler than your target water temperature, you may need more. Use this calculator for a precise recommendation.
Should I use two heaters instead of one?
For tanks over 60 gallons, using two smaller heaters is recommended. This provides more even heat distribution and backup heating if one heater fails, protecting your fish from dangerous temperature drops.