Weight · Seawater
How much does seawater weigh?
8.56 lb/gal · 1.03 kg/L · specific gravity 1.025.
—
| Volume | Pounds | Kilograms |
|---|---|---|
| 1 gal | 9 lb | 4 kg |
| 5 gal | 43 lb | 19 kg |
| 55 gal | 471 lb | 214 kg |
| 100 gal | 856 lb | 388 kg |
| 275 gal | 2,354 lb | 1,068 kg |
| 330 gal | 2,825 lb | 1,281 kg |
| 500 gal | 4,280 lb | 1,941 kg |
| 1,000 gal | 8,560 lb | 3,883 kg |
| 5,000 gal | 42,800 lb | 19,414 kg |
Basis
Standard 35 g/kg ocean salinity, UNESCO equation of state — about 2.5% heavier than fresh water. Liquid weight excludes the container — add tare weight for transport math. Matching tank charts: 55 gal tank · 275 gal tank · 330 gal tank · 500 gal tank · 1000 gal tank.
FAQ
How much does a gallon of seawater weigh?
8.56 lb/gal. That is 1.03 kg per litre (SG 1.025).
How much does a 55-gallon drum of seawater weigh?
About 471 lb of liquid, plus roughly 40–50 lb for a steel drum. A brim-full drum actually holds ~57.7 gal — see the drum chart.
Does temperature change this?
Yes — liquids expand when warm. Hydrocarbons move roughly 0.4% per 10°F; the figure here is the standard reference temperature value.