Square Mile to Square Inch

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.

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.

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.

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.

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.

PSI (pounds of force per square inch) is used for tire pressure in the US because the imperial measurement system was standard in American manufacturing when pneumatic tires were developed in the 1890s. A car tire at 32 psi means 32 lbs of air pressure pushing on every square inch of the tire's inner surface. Europe uses bar (1 bar ≈ 14.5 psi) and some countries use kPa (100 kPa ≈ 14.5 psi).

Screen diagonal (the common marketing metric) is not proportional to area — a 14-inch screen is not twice the area of a 7-inch screen. Area depends on aspect ratio too. A 16:9 display: 14" diagonal → 83 in²; 7" diagonal → 21 in². Comparing in² reveals that a 14" laptop screen has 4× the area of a 7" tablet — useful when evaluating workspace or text readability.

The US uses the 8.5×11 inch letter format (93.5 in²) inherited from colonial British practices. Europe standardized on ISO 216 (A4 = 210×297 mm = 623.7 cm²) in the 1970s, which has the elegant property that each A-series sheet is exactly half the next size up. The US has never adopted ISO paper sizes despite several attempts, partly due to printer industry inertia and the cost of replacing standardized forms.

Torque is force × distance (not force per area), so it is not measured in in². However, engine displacement in the US is sometimes expressed in cubic inches (for classic cars), and engine power in the US context uses lb-ft of torque and horsepower. A V8 engine at 350 cubic inches (5.7 L) displacement might produce 350 lb-ft of torque — a numerically coincidental pairing that became culturally iconic.

Yes, in US aerospace, defense, and mechanical engineering. ANSI/ASME Y14.5 dimensioning standards use inches; cross-sections of structural members and weld areas are expressed in in². US Defense Department specifications (MIL-SPEC) use imperial units. NASA famously lost the Mars Climate Orbiter in 1999 when one engineering team used lbf·s (pound-force seconds) and another used N·s, causing a trajectory error — illustrating the real cost of mixed unit systems.