How much does water weigh?
Enter a volume in US gallons, UK gallons, litres, cubic feet or cubic metres. You'll get the weight of water in pounds, kilograms, short tons and metric tonnes — instantly.
100kg
0.100 metric tonnes · 220 lb
Using standard engineering density: 1,000 kg/m³ (1 kg/L) — the value used by structural engineers, ASHRAE, and plumbing codes for water load calculations.
Common questions
- How much does a gallon of water weigh?
- One US gallon of water weighs 8.34 lb (3.79 kg). One UK (imperial) gallon weighs 10.02 lb (4.55 kg). The difference is because a UK gallon is larger — 4.546 litres vs 3.785 litres for a US gallon.
- How much does a litre of water weigh?
- One litre of water weighs 1 kg (2.20 lb). This is the standard engineering value — water has a density of 1,000 kg/m³ (or 1 kg/L) at near-standard temperatures, which is what structural tables, plumbing codes, and ASHRAE use for load calculations.
- How much does a cubic foot of water weigh?
- One cubic foot of water weighs 62.4 lb (28.3 kg). Since 1 ft³ = 28.317 litres and water weighs 1 kg/L, you get 28.3 kg. Multiply by 2.205 to convert to pounds.
- How much does 5 gallons of water weigh?
- Five US gallons of water weigh 41.7 lb (18.9 kg). This is a common question because a 5-gallon bucket of water is a frequent jobsite load — useful for ergonomic planning and structural checks.
- How much does 100 gallons of water weigh?
- 100 US gallons of water weigh 834 lb (378 kg). At 500 gallons — a common water storage tank — the water alone weighs 4,170 lb (1,893 kg), plus the empty tank weight. This is why full water tanks require structural support calculations.
Want the full explanation and reference tables? Read the water weight guide →
Reference & education only. Not professional, engineering, or code-compliance advice. Estimates are based on published model codes; local amendments and your Authority Having Jurisdiction (AHJ) govern. Always verify against the current adopted code and a licensed professional before doing work.
Last reviewed 2026-09.