Welcome to our immersed weight calculator! If you've ever wondered why objects feel lighter when submerged in water, you'll get your answer here. This immersed weight calculator will help you determine the apparent weight of an object when submerged in any fluid. The calculator has twelve built-on fluids, but you can also input any custom fluid you're interested in studying.

When objects are immersed in a fluid, such as water, the object displaces a volume of the fluid. This displaced fluid exerts an upward force on the object, giving the impression that it has become lighter. Keep reading to find out:

  • What immersed weight is;

  • How buoyant force affects apparent weight; and

  • How to calculate the apparent weight of an object immersed in water or any fluid.

What is immersed weight? – Why does weight change when immersed in water?

If you've ever gone swimming, you've probably noticed feeling lighter while in the water. Why is this? Your mass and volume remain the same, but the water exerts an upward force that counteracts the weight of your body. This force is known as the buoyancy or buoyant force, and it's directly proportional to the volume displaced by the submerged object and the density of the fluid.

This is related to Archimedes' principle. Check our Archimedes' principle calculator to read more!

Immersed weight measures an object's weight when it's fully (or partially) submerged in a fluid. We can easily determine it by subtracting the buoyant force from the object's weight (measured outside):

Immersed weight = Object’s weight - Buoyant force\footnotesize \text{Immersed weight = Object's weight - Buoyant force}

How to calculate the apparent weight – Calculate weight in water

From the previous section, we can see that, for example, if we had an object that weighs 10 kg10 \text{ kg} outside the fluid, and if once we submerge it displaces 2 liters2 \text{ liters} of water, then its immersed weight would be of 8 kg8 \text{ kg}. Not sure about this calculation? Let's go step-by-step:

From the previous section, we can see that, for example, if we had an object that weighs 10 kg10 \text{ kg} outside the fluid and displaces 2 liters2 \text{ liters} of water once submerged, then its immersed weight would be of 8 kg8 \text{ kg}. Not sure about this calculation? Let's go step-by-step:

1. First, we calculate the object's weight:

Object weight=Object mass ×gObject weight=10 kg ×9.8 m/s2Object weight=98 N\footnotesize \begin{split} \text{Object weight} &= \text{Object mass } \times g \\ \text{Object weight} &= \text{10 kg } \times 9.8 \text{ }\mathrm{m/s^2} \\ \text{Object weight} &= 98\text{ N} \end{split}

where gg represents the gravitational acceleration constant of 9.8 m/s29.8 \text{ }\mathrm{m/s^2} or 32.17  ft/s232.17  \text{ }\mathrm{ft/s^2}.

2. Determine buoyancy or buoyant force. For this, we use the following equation:

Buoyant force=ρfluid×Vdisplaced×g\footnotesize \text{Buoyant force} = \rho_\text{fluid}\times V_{displaced}\times g

Where ρfluid\rho_{\text{fluid}} is the density of the fluid and VdisplacedV_\text{displaced} is the volume displaced by the immersed object. Since we are working with water, then the density of the fluid is 1000 kg/m31000 \text{ }\mathrm{kg/m^3}, and the displaced volume is of 2 l2 \text { l} or 0.002 m30.002 \text{ } \mathrm{m^3}. By substituting these:

Buoyant force=1000 kg/m3×0.002 m3×9.8 m/s2Buoyant force=19.6 N\footnotesize \begin{split} \text{Buoyant force} &= 1000 \text{ }\mathrm{kg/m^3} \times 0.002 \text{ }\mathrm{ m^3} \times 9.8 \text{ }\mathrm{m/s^2}\\ \text{Buoyant force} &= 19.6 \text{ N} \end{split}

You can find a more in-depth explanation of buoyancy and the buoyant force formula at the buoyancy calculator!

3. All that's left is to substitute these values in the initial immersed weight expression:

Immersed weight=98 N19.6 N=78.4 N\footnotesize \text{Immersed weight} = 98\text{ N} - 19.6 \text{ N} = 78.4 \text{ N}

We see that object's weight went from 98 N98 \text{ N} to 78.4 N78.4 \text{ N}, or from 10 kg10\text{ kg} to 8 kg8 \text{ kg}. This example calculates the weight in water, but the same concept can be applied to any other liquid. The main difference would be related to the density of the fluid. Jump to our density calculator to find out what density is and density values for different materials.

How much do I weigh in water?
What would your weight be when fully immersed in water if the average density of a human's body is of 1010 kg/m31010 \text{ }\mathrm{kg/m^3}? Do you float, or do you sink? 🤔

Using the immersed weight calculator to calculate apparent weight

Have you ever wondered what your immersed weight is in water, seawater, or honey? With the immersed weight calculator, you can get the submerged weight of any object in up to twelve different fluids. You can also use this tool to verify the results from immersed weight experiments. Let's a simple step-by-step on how to use this tool:

  1. In the Object properties section, input the Object volume and the Object weight.

  2. Right away, the calculator will display the Immersed weight of the object in twelve different substances, including water, gasoline, seawater, vegetable oil, and more.

    Note that if your result is negative, this indicates that the object floats in that particular fluid. This is the case when the density of the liquid is greater than the object's density.

  3. To find the immersed weight in a fluid not listed, go to the Custom liquid section and enter the Liquid density, and the calculator will show the Immersed weight in liquid and Buoyancy.

🙋 For immersed weight experiments, you might need to use a ballast to submerge a light object. In that case, indicate the Ballast volume and the (Ballast + Object) volume. The calculator will provide the Objects volume, which you can use for your immersed weight calculations.

Gabriela Diaz
Object properties
Object volume
cu in
Object weight
Immersed weight (negative values means it will float)...
in gasoline
in rubbing alcohol
in baby oil
in vegetable oil
in water
in sea water
in milk
in dish soap
in corn syrup
in maple syrup
in honey
in mercury
Ballast properties
Ballast volume
cu in
(Ballast + Object) volume
cu in
Custom liquid
Liquid density
oz/cu in
Immersed weight in liquid
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