Formula used
Mass: m = ρ × V
Weight force: F = m × g
Net water mass: mnet = mgross − mtare
Filled volume: Vfilled = Vcapacity × fill percentage
Density links water volume and mass. Gravity converts mass into force. Temperature can slightly change water density.
How to use this calculator
- Choose the required calculation mode.
- Enter volume, mass, dimensions, fill, or tare values.
- Select water type, temperature, and salinity.
- Choose Earth, Moon, Mars, or custom gravity.
- Set decimal precision and press Calculate.
- Copy, print, or export the completed results.
Example data
| Example | Input | Approximate result |
|---|---|---|
| One liter freshwater | 1 L at 20°C | About 0.998 kg |
| One US gallon | 1 US gal at 20°C | About 3.78 kg |
| Rectangular tank | 2 m × 1 m × 1 m, 75% | About 1,497 kg |
| Tare subtraction | 12 kg gross, 2 kg tare | 10 kg water |
Water weight reference table
Values below use freshwater near 20°C. Actual results vary slightly. Temperature and salinity affect density.
| Volume | Approximate mass | Approximate Earth force |
|---|---|---|
| 1 mL | 0.998 g | 0.00979 N |
| 1 L | 0.998 kg | 9.79 N |
| 1 US cup | 0.236 kg | 2.31 N |
| 1 US gallon | 3.78 kg | 37.1 N |
| 1 Imperial gallon | 4.54 kg | 44.5 N |
| 1 cubic foot | 28.27 kg | 277.2 N |
| 1 cubic meter | 998.2 kg | 9.79 kN |
Frequently asked questions
How much does one liter of water weigh?
One liter weighs about one kilogram. Temperature causes small density changes. The calculator applies the selected settings.
How much does one US gallon weigh?
One US gallon weighs about 8.34 pounds. This estimate assumes ordinary freshwater. Warmer water weighs slightly less.
Does seawater weigh more than freshwater?
Yes, dissolved salts increase seawater density. Salinity changes the final result. Enter local salinity when available.
Are mass and weight the same?
Mass measures matter in kilograms. Weight is gravitational force in newtons. Gravity changes force, not mass.
Why does temperature affect water weight?
Temperature changes water density. Equal volumes can contain different masses. The change is usually small.
Can this calculate a partially filled tank?
Yes, use percentage or water depth. Depth formulas support listed shapes. Remaining capacity appears with results.
Does horizontal cylinder depth work automatically?
Yes, the calculator uses circular segment geometry. Enter internal diameter and length. Then provide actual water depth.
Can I subtract container weight?
Use the tare calculation mode. Enter gross and empty masses. The calculator returns net water mass.
Can I use custom liquid density?
Yes, select custom density. Enter kilograms per cubic meter. This also supports other liquids.
Can I calculate Moon or Mars weight?
Yes, choose the gravity preset. Water mass remains constant. The displayed force changes accordingly.
How accurate are the results?
Results depend on entered measurements. Density models are practical estimates. Use certified data for critical engineering.
Assumptions and limitations
This tool estimates density using temperature and salinity. It assumes ordinary pressure conditions. Verify safety-critical loads with qualified engineering guidance.