Acre to Square Mile
ac
mi²
Conversion History
| Conversion | Reuse | Delete |
|---|---|---|
1 ac (Acre) → 0.0015625 mi² (Square Mile) Just now |
Quick Reference Table (Acre to Square Mile)
| Acre (ac) | Square Mile (mi²) |
|---|---|
| 0.25 | 0.000390625 |
| 1 | 0.0015625 |
| 5 | 0.0078125 |
| 40 | 0.0625 |
| 160 | 0.25 |
| 843 | 1.3171875 |
| 10,000 | 15.625 |
About Acre (ac)
An acre is a US customary and imperial unit of land area equal to 4,046.86 m², 43,560 ft², or approximately 0.405 hectares. It remains the primary unit for agricultural and rural land transactions in the United States and is still used in the UK for real estate. One acre is roughly the size of an American football field (without end zones). A typical suburban lot in the US is 0.1–0.5 acres; a small farm might be 40–160 acres. An acre is not tied to any particular shape — it can be long and narrow or square (about 209 × 209 feet).
An American football field (without end zones) is about 1 acre. A typical suburban lot is 0.25 acres. Central Park is roughly 843 acres.
Etymology: From Old English 'æcer' (open field), related to Latin 'ager' and Greek 'agros' (field). Originally defined as the amount of land a yoke of oxen could plow in one day. The acre was standardized in England under Edward I in 1305 as 40 perches long by 4 perches wide, giving the 4,840 yd² (43,560 ft²) definition still used today.
About Square Mile (mi²)
A square mile (mi²) is a large imperial unit of area equal to 640 acres or approximately 2.59 km², used primarily in the United States for land area of counties, cities, and states. New York City covers about 303 mi²; Texas is roughly 268,596 mi². In the US, the Public Land Survey System divides land into townships of 36 mi² and sections of 1 mi². Population density in US contexts is often reported as people per square mile. The unit is not used in official international statistics, where km² is the standard.
Manhattan island is about 23 mi². The state of Texas is roughly 268,596 mi². A standard US township is 36 mi².
Acre – Frequently Asked Questions
Why is an acre such an odd number — 43,560 square feet?
It derives from medieval strip-farming geometry: a furlong (220 yards, the distance a team of oxen could plow without resting) by a chain (22 yards, the surveyor Gunter's 1620 chain length). 220 × 22 = 4,840 yd² = 43,560 ft². The chain and furlong system was designed so 10 acres = 1 furlong × 1 chain × 10 = 1 furlong × 1 furlong ÷ 10, creating a practical survey grid. The awkward ft² number is just a consequence of translating yards to feet.
How many acres does a typical US farm have?
The average US farm is about 445 acres, but this number is skewed by enormous industrial operations. The median farm is closer to 80 acres. Corn and soybean farms in the Midwest average 400–600 acres. Cattle ranches in the West can span tens of thousands of acres. The largest single farm in the US (Farmland LP holdings) exceeds 150,000 acres. The USDA classifies a "small family farm" as under 230 acres.
Why did medieval English farmers define the acre as a furlong by a chain?
A furlong (660 ft) was the length an ox team could plow before resting, and a chain (66 ft) was the width of one plow strip. Together they made an acre — the area one team could plow in a day. This explains the odd 43,560 ft² figure: 660 × 66 = 43,560. The furlong and chain are obsolete, but their product lives on in every US land deed, making the acre a fossilized record of medieval English agriculture baked into modern American law.
How long would it take to walk the perimeter of 1 acre?
If the acre is square (209 × 209 ft ≈ 63.6 × 63.6 m), the perimeter is 836 ft ≈ 255 m. At a 4 mph walking pace (5.9 ft/s), that takes about 142 seconds — roughly 2.5 minutes. An acre shaped as a long narrow strip 1 ft × 43,560 ft would have a perimeter of 87,122 ft (~16.5 miles) — illustrating that perimeter depends entirely on shape, not area.
What US states still use acres in official land descriptions?
All 50 US states use acres in official property descriptions under the Public Land Survey System (PLSS). Federal land management (BLM, USFS, National Parks) reports in acres; the National Park Service, for example, manages 85 million acres. The PLSS sections (640 acres each) underlie virtually all western US real estate titles. Switching to hectares would require re-recording tens of millions of deeds — essentially impossible politically.
Square Mile – Frequently Asked Questions
Why does the US still use square miles for land area?
The Public Land Survey System (PLSS), established by the Land Ordinance of 1785, divided US territory into 6-mile × 6-mile townships (36 mi²) and 1-mile × 1-mile sections (1 mi², = 640 acres). This grid underlies property deeds, county boundaries, and road layouts across most of the western US. Switching to km² would require legal redefinition of millions of property descriptions — a transition with no political appetite.
Is Manhattan really 23 square miles?
Manhattan borough is 22.83 mi² (59.1 km²), making it one of the most densely populated places on Earth at about 71,000 people/mi². The island itself (excluding water area) is about 13.4 mi². For comparison, the entire city of New York is 302.6 mi², of which 36% is water. Central Park occupies about 1.3 mi² — nearly 6% of Manhattan's land area.
Which US state is the largest by square miles?
Alaska is by far the largest at 663,268 mi² — over twice the size of Texas (268,596 mi²). Alaska is so large it would be the 18th largest country in the world if independent. For perspective, the entire Lower 48 states fit within Alaska about 5 times over in land area. Alaska also has the longest coastline of any US state at 33,904 miles.
How big is one square mile in everyday terms?
One square mile is a square about 1,609 m (just over a mile) on each side. A standard city grid: in Chicago, the city blocks are laid out on a 1-mile square grid, so 16 standard blocks (4 × 4) = 1 mi². Walking the perimeter of 1 mi² takes about 1 hour at a moderate pace. In rural areas, US county road grids typically run every mile, creating a visible 1 mi² checkerboard visible from aircraft.
What is the US Public Land Survey System and why is it based on square miles?
The PLSS divides most land west of the Appalachians into a grid of 6×6 mile townships, each split into 36 sections of 1 mi² (640 acres). Established by the Land Ordinance of 1785, it still defines property boundaries for roughly 1.5 billion acres across 30 states. County roads in the Midwest often follow PLSS section lines, creating the visible checkerboard pattern from the air. The system predates metric adoption and is so embedded in US land titles that converting to km² would require re-recording tens of millions of deeds.