How Much Does a Gallon of Water Weigh?
You need a quick number, so here it is: one U.S. gallon of water weighs about 8.33 pounds (3.78 kilograms) at room temperature, often rounded to 8.34 pounds.
That figure comes from water's density, which sits very close to 1 gram per milliliter at 68°F (20°C). According to the USGS Water Science School, weight and density are among water's most fundamental physical properties, and the ones most people actually need for everyday math.
The rounded 8.34 number is an approximation, though. Three things nudge it up or down: temperature, dissolved minerals, and (barely) altitude. Below you'll find weight charts for every common volume, from a single cup to a 55-gallon drum, plus a plain explanation of what makes water heavier or lighter.
Key Takeaways
About 8.33 Pounds Per Gallon
Storage Weight Adds Up Fast
Water Weight by Volume: Quick Reference Charts
These charts give you a fast lookup for the most common water volumes. All weights assume room temperature (68°F / 20°C) and standard pressure.
Common U.S. Measurements (Imperial)
| Volume | Weight (lbs) | Weight (oz) |
|---|---|---|
| 1 cup (8 fl oz) | 0.52 lbs | 8.3 oz |
| 1 pint (16 fl oz) | 1.04 lbs | 16.7 oz |
| 1 quart (32 fl oz) | 2.09 lbs | 33.4 oz |
| Half-gallon (64 fl oz) | 4.17 lbs | 66.7 oz |
| 1 gallon (128 fl oz) | 8.34 lbs | 133.5 oz |
| 2 gallons | 16.68 lbs | 267 oz |
| 5 gallons | 41.7 lbs | 667 oz |
| 10 gallons | 83.4 lbs | 1,335 oz |
Metric Measurements
| Volume | Weight (kg) | Weight (lbs) |
|---|---|---|
| 100 mL | 0.1 kg | 0.22 lbs |
| 250 mL | 0.25 kg | 0.55 lbs |
| 500 mL | 0.5 kg | 1.1 lbs |
| 1 liter | 1.0 kg | 2.2 lbs |
| 2 liters | 2.0 kg | 4.4 lbs |
| 5 liters | 5.0 kg | 11.0 lbs |
| 10 liters | 10.0 kg | 22.0 lbs |
Common Containers
| Container | Volume | Water Weight | Total Weight (approx.) |
|---|---|---|---|
| Standard water bottle | 16.9 fl oz (500 mL) | 1.1 lbs | About 1.12 lbs (bottle adds roughly 0.5 oz) |
| 1-gallon jug | 128 fl oz | 8.34 lbs | About 8.5 lbs with the jug |
| 5-gallon cooler jug | 640 fl oz | 41.7 lbs | About 43 lbs with the container |
| 55-gallon drum | 7,040 fl oz | 458.7 lbs | About 480 lbs with a steel drum |
How Temperature Changes the Weight of Water
Cold water weighs more than hot water. The difference is small, but it's real and measurable.
Water reaches its peak density at 39.2°F (4°C). At that temperature, the molecules pack together as tightly as they ever will. Heat the water up and they start moving faster and spreading apart, so the same gallon takes up a touch more space and weighs a touch less. The American Chemical Society puts it simply: heating a substance makes its molecules speed up and spread out, occupying a larger volume and lowering the density.
Here's how the weight of one gallon shifts across common temperatures:
| Temperature | Density (g/mL) | Weight per Gallon (lbs) |
|---|---|---|
| 32°F (0°C), ice-cold | 0.99987 | 8.344 |
| 39.2°F (4°C), peak density | 1.00000 | 8.345 |
| 68°F (20°C), room temp | 0.99821 | 8.330 |
| 100°F (37.8°C), hot tap | 0.99224 | 8.280 |
| 150°F (65.6°C), hot | 0.98021 | 8.180 |
| 212°F (100°C), boiling | 0.95840 | 7.996 |
The gap between ice-cold water and boiling water is about 0.35 pounds per gallon, roughly 4 percent. For cooking or hauling, that's nothing. For precise work in plumbing, industrial systems, or a lab, it's the kind of detail that matters.
What Else Affects the Weight of Water?
Temperature is the biggest variable, but dissolved minerals change the number too.
Your tap water is not pure H2O. It carries minerals like calcium, magnesium, and sodium, measured together as TDS (total dissolved solids). The EPA's secondary drinking-water guideline for TDS is 500 mg/L, a taste and appearance benchmark rather than a health-based limit (EPA Secondary Drinking Water Standards).
At normal tap-water levels, TDS adds only a fraction of an ounce per gallon. You notice it in taste, scale, and spotting long before you notice it on a scale. That is where a TDS guide or water test helps more than a weight conversion.
For cooking, storage, emergency planning, and lifting, use 8.34 pounds per gallon. For lab work or engineered systems, use temperature-specific density.
Water Weight in Real Life: Why It Matters
Water weight matters most when you have to store it, carry it, or support it.
Emergency Storage
Ready.gov recommends storing at least one gallon of water per person per day for drinking and sanitation. For a family of four planning a three-day supply, that is 12 gallons, or roughly 100 pounds of water before containers.
If your local utility issues a notice, the same one-gallon-per-person-per-day rule is the baseline. Our boil-water advisory guide explains what to do with stored water, tap water, and filters during an advisory.
Around the House
A 5-gallon cooler jug is about 41.7 pounds of water, plus the bottle. A 40-gallon water heater holds about 334 pounds of water before the tank itself. An aquarium, rain barrel, or storage drum can become a structural load quickly.
How Water Compares to Other Liquids
Water isn't the heaviest liquid in your kitchen, or your garage. Here's how some common ones stack up per gallon:
| Liquid | Weight per Gallon (lbs) | Compared to Water |
|---|---|---|
| Honey | About 12.0 lbs | 44% heavier |
| Milk (whole) | About 8.6 lbs | 3% heavier |
| Water | 8.34 lbs | baseline |
| Olive oil | About 7.6 lbs | 9% lighter |
| Gasoline | About 6.1 lbs | 27% lighter |
Milk edges out water because it's basically water carrying extra cargo: dissolved fats, sugars, and proteins. Gasoline is lighter because hydrocarbons are less dense than water molecules. Honey is the heavyweight, with a density nearly 1.5 times that of water, which is exactly why it pours so slowly.
Know what's in your water, beyond just its weight.
Dissolved minerals, metals, and contaminants shape your water's taste, safety, and how it affects your home. Crystal Quest water test kits give you a clear picture, and our filtration systems are engineered and built in the USA.
Frequently Asked Questions About Water Weight
How much does a 5-gallon jug of water weigh?
A 5-gallon jug of water weighs about 41.7 pounds, and that's the water alone. Add 1 to 2 pounds for the plastic container, and you're carrying roughly 43 to 44 pounds total. That's the typical weight of a home water cooler bottle.
How much does a bottle of water weigh?
A standard 16.9 fl oz water bottle holds about 1.1 pounds of water. The plastic bottle adds roughly half an ounce, bringing the total to just over 1.1 pounds. A larger 1-liter bottle holds about 2.2 pounds of water.
How much does a cup of water weigh?
One cup of water (8 fluid ounces) weighs about 0.52 pounds, just over half a pound. That tracks with the standard kitchen measure: 1 cup of water is roughly 236 mL, or about 236 grams. Eight cups a day add up to about 4.2 pounds of water.
How much does a liter of water weigh?
One liter of water weighs 1 kilogram (2.2 pounds) at room temperature. It's one of the most convenient conversions in the metric system, and it was designed that way. The weight shifts slightly above or below room temp, but 1 kg per liter is accurate enough for almost any practical use.
Is a gallon of milk heavier than a gallon of water?
Yes. A gallon of whole milk weighs about 8.6 pounds, compared with water's 8.34 pounds. Milk is denser because it carries dissolved fats, proteins, and sugars (lactose) that add mass without adding much volume.
Does water weigh more when it's frozen?
No. Ice weighs the same as the water it came from, because the total mass doesn't change. Ice does take up about 9 percent more space, since water molecules lock into a crystal structure as they freeze. That's why ice floats: it's less dense, not lighter.
Is water heavier than sand?
Sand is significantly heavier by volume. Dry sand weighs about 100 pounds per cubic foot, while water weighs 62.4 pounds per cubic foot. Even wet sand, which holds water in the gaps between grains, outweighs water alone.
Does hot water weigh less than cold water?
Yes, slightly. As water heats up, its molecules spread apart and density drops. A gallon of boiling water weighs about 8.0 pounds, compared with about 8.33 pounds at room temperature, a difference of about 0.34 pounds. For everyday purposes you'd never notice it.
