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Immersion Heater Wattage Calculator

This tool, part of our collection of articles and tools on how to choose the right immersion heater, will allow you to easily calculate the wattage you need for an immersion heater (tank heater). We have a huge variety of immersion heaters available for online ordering; once you know your wattage, watt density, and sheath material, you can choose any heater from our standard list, or enter your specifications in our configurator to get a 1-day quote on a built-to-order heater.

All wattage totals and subtotals shown include a 20% safety factor.

Units:     Imperial     Metric

Step 1: Find the liquid's properties.

Material Specific Heat Boiling Point Density

Look up properties:

I'll input my liquid's properties:

g • K


Show note

lb / ft³kg / m³

Step 2: Enter the process details for your liquid.

Volume of Liquid Starting Temp. Ending Temp. Time to Reach Temp.
gal.L °F°C °F°C



Total wattage required to raise liquid to operating temperature:

Check here if you will be adding solid objects to this tank. (This opens steps 1a and 2a for properties of your object.) You can uncheck this to remove this subtotal from the total wattage.

Step 1a: Find the solid object's properties.

Material Specific Heat Melting Point Density

Look up properties:

I know the object's thermal properties:

g • K


Show note

lb / ft³kg / m³

Step 2a: Enter the process details for your solid object.

Weight of Solid Temp. When Inserted Temp. When Removed Time Immersed

I know the object's weight:

Calculate from object's dimensions:
× ×

Calculated weight:

°F°C °F°C

Show note



Total wattage required to raise solid object to operating temperature:

Step 3: Find surface area of your tank (for wattage loss calculations).

Tank Shape Tank Measurements Surface Area



Other (or input surface area directly)

Length: ftcm    in.

Width: ftcm    in.

Diameter: ftcm    in.

Height: ftcm    in.

If your tank has an irregular shape, this calculator will not be able to find its surface area. You'll need to take measurements to find the side, top, and bottom surface areas; you can then use them in the calculator by putting them in the next column of this table.

Top: ft²

Sides (total): ft²

Bottom: ft²

Step 4: Find total wattage losses.

Ambient Air Temp. Tank Wall Material Wattage Losses per ft² Total Wattage Losses
°F°C Top:

Total wattage losses from all walls at operating temperature:

Total heating wattage required from immersion heater:

Please note that, while this tool uses the same math we use to calculate wattages, we cannot be liable for incorrect information or misuse of the calculator, and results from this calculator do not constitute a guarantee on any product.