Objects feel lighter underwater because the liquid pushes up on them. Divers, salvage crews and anyone lifting things from a pool experience this. In mercury, even iron floats.
How to use the Immersed Weight Calculator
- Mass in air
- Volume
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Enter the object’s weight (mass) in air and its volume.
Inputs explained
| Field | What to enter |
|---|---|
| Mass in air | Units: kg, g, mg, t, lb, oz |
| Volume | Units: L, mL, m³, US gal, ft³ |
What each result means
- Object density = [Mass in air]÷[Volume]
- Apparent mass in fresh water = [Mass in air] – 998.2×[Volume]
- Apparent mass in seawater = [Mass in air] – 1025×[Volume]
- Apparent mass in ethanol = [Mass in air] – 789×[Volume]
- Apparent mass in gasoline = [Mass in air] – 745×[Volume]
- Apparent mass in olive oil = [Mass in air] – 911×[Volume]
- Apparent mass in glycerine = [Mass in air] – 1261×[Volume]
- Apparent mass in mercury = [Mass in air] – 13534×[Volume]
Example values
How the main result changes when Mass in air changes and everything else stays at the example values above:
| Mass in air (kg) | Apparent mass in fresh water (kg) |
|---|---|
| 5 | 3.7323 |
| 7.5 | 6.2323 |
| 10 | 8.7323 |
| 12.5 | 11.2323 |
| 15 | 13.7323 |
| 20 | 18.7323 |
Formula
W_immersed = W_air − ρ_liquid·g·V
Worked example
Inputs — Mass in air: 10 kg; Volume: 1.27 L.
Results — Object density = 7,874.01575 kg/m³; Apparent mass in fresh water = 8.73229 kg; Apparent mass in seawater = 8.69825 kg; Apparent mass in ethanol = 8.99797 kg; Apparent mass in gasoline = 9.05385 kg; Apparent mass in olive oil = 8.84303 kg; Apparent mass in glycerine = 8.39853 kg; Apparent mass in mercury = -7.18818 kg.
Key terms
- Apparent weight
- Weight minus buoyant force.
Frequently asked questions
Why does a negative value appear?
The object would float – the liquid can support more than its weight.
Why does iron float in mercury?
Mercury is denser than iron.
Is apparent mass the same as true mass?
No – true mass doesn't change; only the supporting force does.
How do divers use this?
Weight belts are chosen to give slightly negative buoyancy.