# How Much Does a Gallon of Water Weigh? Easy Calculation

Question: How much does a gallon of water weigh?

Ever wonder how much a gallon of water weighs? A US gallon is 8.34 lbs or 3.78 kg. (David Mulder)

Answer: A US gallon of water weighs 8.34 lbs or 3.78 kg at 62 °F (17 °C). An imperial gallon (UK) weighs 10.022 lbs or 4.546 kg, at its most dense temperature, which is 2.20456 lbs / L at 4 °C or 39 °F.

Ballpark Calculation (for all temperatures)

1 gallon is about 3.75 liters
1 liters = 1 kilogram (density of water is 1 kg/liter)
1 kg is about 2.2 lbs
so, 3.75 kg is about 8.25 lbs and 1 gallon is about 8.25 lbs

### Three Different Units of Gallon

It makes a difference which unit of gallon you are using. There are two US definitions of gallon. The US liquid gallon (most commonly used) is defined as 231 cubic inches, which is 3.785 liters, and weighs 8.344 lbs at its highest density.

The US dry gallon is defined as 1/8th of a US bushel, which is 268.8025 cubic inches or 4.405 L. The weight of a US dry gallon is 9.711 lbs of water at its highest density.

The UK gallon or imperial gallon originally was defined as 10 lbs of water, but the modern definition is exactly 4.54609 L or 10.02 lbs of water at its maximum density.

### Effect of Water Temperature on Weight

Cold water is more dense than ice or than warm water or liquid just above freezing. This is an unusual property of the substance, resulting from hydrogen bonding. So, a gallon of warm water would weigh slightly less than a gallon of cold water. The exact difference would depend on the temperatures in question, but it doesn’t affect the value by much.

Of course, gravity affects weight too, so a gallon of water (or anything else) would weigh more on Jupiter than on Earth, while it would weigh less on the Moon than Earth.

### Easy Way To Remember the Weight of Water

While you’ll want to keep the exact volume definitions in mind for scientific calculations, for everyday use you can remember the weight of water using the simple rhyme: A pint’s a pound, the world round.

The saying refers to the rough equivalence between 16 fluid ounces (a pint) and 16 ounces avoirdupois weight. A gallon is 4 quarts or 8 points, so a gallon weighs approximately 8 lbs.

# Today In Science History – August 4 – Phoenix Mars Lander

Artist’s impression of the Phoenix Mars lander shutting down operations for the Martian winter. Credit: NASA/JPL

On August 4, 2007 the Phoenix Mars lander was launched from Earth to land on the surface of Mars. It was sent in response to the Mars Odyssey Orbiter’s discovery of the possibility of finding ice under the polar surface of Mars. Odyssey’s sensors detected a gamma ray signature from hydrogen concentrated around Mars’ north pole during its mission. Phoenix would go there to find out.

The Phoenix Mars mission was the first of NASA’s Scout program. This program was intended to send small, relatively inexpensive missions to Mars. The general plan for the lander was to answer three questions: can the Martian Arctic region support life? Is there any history of water in the region? and How does the Arctic climate affect the rest of Mars?

The lander itself was a platform of scientific equipment including ovens, mass spectrometers, a ‘chemistry lab in a box’ unit to analyze soil samples scooped up by the lander’s robotic arm. Other equipment included a meteorological station and an atomic force microscope.

Phoenix landed on Mars on May 25, 2008 and began soil experiments. The robotic arm from the lander scraped a shallow trench in the soil exposing a shiny substance that was later proved to be water ice. NASA announced the discovery of water ice on Mars late July 2008.

# Element Symbols – Symbols For Earth, Air, Fire and Water

These are the four ancient element symbols for earth, air, fire and water. Each symbol is shown with a color associated with each element with a stylized background pertaining to each element.

The colors green and brown are often associated with the element earth.
Bright blue, white, yellow and gray are colors that apply to the element air.
Fire, like flames, is orange or red.
Blue is the color of water.

These symbols can found without the backgrounds in Earth, Air, Fire and Water Element Symbols.
They can also be found without background and without colors in Earth, Air, Fire and Water Symbols.

# Earth, Air, Fire And Water Element Symbols

The original four ancient elements for alchemists are earth, air, fire and water. These graphics show the alchemical symbols for each element and the color commonly associated with each.

Earth is generally associated with the colors brown and green.
Air is associated with blue, white, yellow or gray.
Fire is often red or orange.
Water is mostly associated with the color blue.

Uncolored versions of these symbols can be found in Earth, Air, Fire and Water Symbols.
Colored versions with stylized backgrounds can be found in Four Ancient Element Symbols.

# Earth, Air, Fire And Water Symbols

Alchemists considered the all things to be made up of four basic elements: earth, air, fire and water. These are the alchemy symbols for earth, air, fire and water.

The ancient Greek philosopher Plato further defined the four elements by adding two qualities to each element. There were four possible qualities: hot, cold, wet, and dry.

Earth has the qualities dry and cold.
Air is wet and hot.
Fire is both hot and dry.
Water is wet and cold.

These elements would appear in discussions of chemical science well into the 18th Century when elements were still referred to as airs for gasses and earths for minerals and metals. Now we know these ancient elements are really substances that are made up of elements rather than being elements themselves.

Colored versions of these symbols can be found in Earth, Air, Fire and Water Element Symbols. Colored versions with stylized backgrounds can be found in Four Ancient Element Symbols.

# Water Ocean Found on Enceladus

Artist rendition of Saturn’s Moon Enceladus suggesting liquid water ocean under the ice crust. NASA/JPL

Researchers involved with the Cassini-Huygens Saturn Mission announced evidence of the existence of a liquid water ocean under the frozen surface of one of Saturn’s moons.

Water was first detected back in 2005 when the Cassini spacecraft discovered ice and water vapor venting from Enceladus’ South Pole. Further investigation of the gravity data provided by Cassini suggests a large body of water under 30 or 40 kilometers of the moon’s ice crust. Their findings were published in the April 4, 2014 edition of Science.

The discovery of liquid water has piqued interest in what could be swimming in that water. Along with water, the vapor jets contained evidence of salt and organic compounds. Could microbial life exist on a moon only 500 miles in diameter? At the very least, the discovery expands the definition of ‘habitable zone’.