Acre-Feet (acre-foot) to Glas (glas) conversion

What is the Acre-Foot?

The acre-foot is a unit of volume equal to the amount of water needed to cover one acre of land to a depth of one foot. It is the standard measure used for large-scale water resources in the United States, including reservoirs, irrigation supplies, and municipal water rights.

Definition

One acre-foot is defined as the volume of a prism with a base area of one acre (43,560 square feet) and a height of one foot, giving exactly 43,560 cubic feet.

$$1\ \text{acre-foot} = 1.23348 \times 10⁶\ \text{l}$$

Because the US survey foot and the international foot differ slightly, the acre-foot is fixed by its exact defining relation of 43,560 cubic feet, which equals about 1,233.48 cubic metres or 1,233,482 litres; the NIST Guide to the SI tabulates the acre-foot as 1.233 489 × 10³ m³.

Origin and History

The acre-foot arose in the American West during the late 19th and early 20th centuries, as irrigation districts and water agencies needed a practical unit for measuring large volumes of stored and delivered water. It combines the acre, an old English unit of land area, with the foot of depth, making it intuitive for engineers estimating how much water a given area of reservoir or flooded field holds.

Law and Notable Facts

The acre-foot remains the legal and administrative unit for water rights, reservoir capacity, and interstate water compacts throughout the western United States. A commonly cited rule of thumb is that one acre-foot supplies roughly one to two typical American households for a year, which is why it is used to describe how many homes a reservoir can serve.

Real-World Examples and Conversions

• A single acre-foot equals about 325,851 US gallons of water.
• Lake Mead, the largest reservoir in the US, has a capacity of roughly 28.9 million acre-feet when full.
• An Olympic swimming pool holds about 2,500 cubic metres, or roughly 2 acre-feet.
• In metric terms, 1 acre-foot is approximately 1,233 cubic metres (1.23348 million litres).

What is Glas?

Glas is a Swedish unit of volume used in cooking and baking. The word "glas" is Swedish for "glass," reflecting its origin as a measure based on the contents of a drinking glass. In modern Swedish recipes it is a standardized measure.

Definition of Glas

In the standardized Swedish system of kitchen measures (matmått), one glas is defined as 2 deciliters, which is equal to 200 millilitres.

$$1 \text{ glas} = 2 \text{ dL} = 200 \text{ mL} = 0.2 \text{ L}$$

Like the other Swedish cooking measures (kryddmått, tesked, matsked, and kaffekopp), the glas follows the metric system, so conversions to litres and millilitres are exact.

Relationship to Other Units

The glas fits neatly into the family of Swedish volume measures and the wider metric system:

• 1 glas = 200 mL = 20 centilitres
• 1 glas = 2 deciliter (dL)
• 1 glas ≈ 6.76 US fluid ounces
• 1 glas ≈ 7.04 Imperial fluid ounces
• 1 glas ≈ 0.85 US cups

Because 1 kaffekopp (coffee cup) is 1.5 dL, a glas (2 dL) is slightly larger than a kaffekopp.

Historical Context

The glas belongs to the set of household measures that Swedish cooks have long used in place of scales. As Sweden adopted the metric system in the late 19th century, these traditional kitchen measures were standardized to round metric values, giving the glas its modern value of 2 dL. There is no single law or historical figure directly associated with it; rather, it reflects the gradual standardization of everyday cooking measurements.

Real-World Examples

Glas measurements appear frequently in Swedish and Scandinavian recipes:

• Baking: A cake recipe might call for 3 glas of flour.
• Cooking: A sauce or soup might need 1 glas of cream or stock.
• Drinks: Punch and cordial recipes are often measured in glas.

Converting Glas

Because the glas is defined in exact metric terms, conversion is straightforward. To convert a volume in glas to litres:

$$\text{Volume in Liters} = \text{Volume in Glas} \times 0.2$$

For example, 4 glas equals $4 \times 0.2 = 0.8$ litres (800 mL).