Aquarium Heater Calculator
Heater wattage for your tank.
Enter your values
ⓘ Live results
Results
- Heater wattage
- 425 W
- Calculated need
- 420 W
- Temperature lift
- 7 °C
- Running cost per month
- $30.24
Quick answer
Aquarium heaters need roughly 2.5 watts per litre for a 5°C lift.
Watts ≈ litres × 0.5 × ΔT
How to use the Aquarium Heater Calculator
- 1Enter your tank volume in litres.
- 2Enter the target water temperature.
- 3Enter the coolest room temperature.
Worked example
Using the values the calculator loads with:
Inputs
- Tank volume120 L
- Target temperature26 °C
- Room temperature19 °C
Results
- Heater wattage425 W
- Calculated need420 W
- Temperature lift7 °C
- Running cost per month$30.24
Frequently asked questions
Should I use two heaters?
Two half-size heaters protect against a stuck-on failure cooking the tank.
Do I need a controller?
An external controller adds a valuable safety layer.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.