Aquarium Heater Calculator
Heater wattage for your tank.
Enter your values
Enter the tank volume in L.
Enter the target temperature in °C.
Enter the room temperature in °C.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- 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
At a glance
| What it does | Heater wattage for your tank. |
|---|---|
| Category | Science |
| Inputs needed | Tank volume, Target temperature, Room temperature |
| Main output | Heater wattage |
| Formula | Watts ≈ litres × 0.5 × ΔT |
| Cost | Free — no sign-up, no download |
How to use the Aquarium Heater Calculator
- 1Enter your tank volume in litres.
- 2Enter the target water temperature.
- 3Enter the coolest room temperature.
Inputs explained
- Tank volume(L)
- Enter the tank volume in L.
- Target temperature(°C)
- Enter the target temperature in °C.
- Room temperature(°C)
- Enter the room temperature in °C.
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.
What do I need to enter into the Aquarium Heater Calculator?
Just 3 values: tank volume, target temperature, room temperature. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Aquarium Heater Calculator work out the answer?
Aquarium heaters need roughly 2.5 watts per litre for a 5°C lift. It applies the formula Watts ≈ litres × 0.5 × ΔT and shows the working so you can check each step by hand.
Is the Aquarium Heater Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.