How Much Does a Gallon of Water Weigh? Pounds & Chart

One U.S. liquid gallon of fresh water weighs roughly 8.34 pounds, or about 3.78 kilograms. Using that estimate, five gallons weighs about 41.7 pounds and ten gallons about 83.4 pounds—before adding the container.

The 8.34 lb-per-gallon figure is a convenient approximation, not an exact constant. Water density changes with temperature and dissolved substances, and an Imperial gallon contains more water than a U.S. gallon.

Unless stated otherwise, every gallon on this page means a U.S. liquid gallon.

For a rough freshwater estimate, use:

Water weight in pounds ≈ U.S. gallons × 8.34

For example, 5 × 8.34 = 41.7 lb. To estimate the volume represented by a known water-only weight, reverse the calculation:

U.S. gallons ≈ pounds ÷ 8.34

So 50 pounds of water is approximately 6.00 U.S. gallons under this same assumption. The comparison is useful alongside our examples of things that weigh 50 pounds.

The more general relationship is mass = volume × density. For a more precise result, use the density of the actual water at its measured temperature and composition, with consistent units.

Every row below is calculated using the same 8.34 lb per U.S. gallon approximation. The displayed decimal places show the multiplication; they do not make the density assumption exact.

These are water-only values. They exclude the jug, bucket, tank, lid, fittings, and anything else stored with the water.

Five U.S. gallons of fresh water is approximately 41.7 lb using the chart's coefficient. A filled container weighs more because the container itself adds mass.

Filled total ≈ water weight + empty container weight

For a hypothetical container measured at 3 lb empty, the estimate would be 41.7 + 3 = 44.7 lb when it contains five gallons. The 3 lb figure is an example input, not a typical weight for every jug or bucket.

A capacity label also does not prove that a container is filled to that volume. Check the actual fill amount. For an exact total for your particular container, weigh it rather than relying on the estimate.

These figures are close approximations with different conditions or rounding. They should not be treated as competing exact definitions.

USGS lists 8.33 pounds per gallon in its water facts, while a USGS hydrology report uses 8.34 pounds per gallon as a conversion relation. University of Georgia Extension gives about 8.32 lb per gallon at 77°F.

The gallon defines volume; it does not define the mass of the contents. Temperature and dissolved material affect density. This page consistently uses 8.34 for its rough freshwater chart rather than mixing coefficients between rows.

When comparing two results, check the gallon type, water conditions, rounding, and whether the container is included.

NIST's conversion tables distinguish the two volume units:

An Imperial gallon is approximately 20.1% larger. For the same water at the same density, it therefore contains approximately 20.1% more mass.

Applying that volume ratio to this page's rough 8.34 lb-per-U.S.-gallon coefficient gives approximately 10.02 lb per Imperial gallon. This is a calculated approximation, not an exact water-weight definition.

Does 5 gallons of water weigh 50 pounds?

No. Five U.S. gallons is about 41.7 lb of water using the stated estimate. Six gallons is about 50.04 lb, before the container.

How much does 20 gallons of water weigh?

Approximately 166.8 lb of water, using 20 × 8.34. Add the actual empty container weight for a filled-total estimate.

How heavy is 100 gallons of water?

Approximately 834 lb of water under the chart's assumption. The tank, fittings, and other contents add their own weight; this figure alone is not an equipment load rating.

Does the shape of the container change the water's weight?

Not if the actual volume and density are unchanged. Five gallons in a wide container and five gallons in a narrow one represent the same volume, although their fill heights differ.

Can I use the chart for saltwater or another liquid?

Not as an accurate conversion. This chart assumes fresh water; another liquid or a different dissolved-material concentration needs its own density.

Are pounds and fluid ounces interchangeable?

No. Pounds measure mass in this context, while fluid ounces measure volume. A volume unit needs a density assumption before you can convert it to a mass.

• USGS hydrology report: water conversion relations: the 8.34 lb-per-gallon reference used for the chart.
• USGS Facts About Water: a general 8.33 lb-per-gallon reference.
• UGA Extension: Weight of Water: temperature-specific example.
• NIST SI conversion tables: U.S. and Imperial gallon volumes.

Chart values are calculated estimates from the stated coefficient. Container weight is excluded unless explicitly added in an example. No measured sample or fixed mass for all water temperatures is claimed.