Square Miles to Square Millimeters (mi² to mm²)

1 square mile equals 2,589,988,110,336 square millimeters exactly.

1 square mile = 2,589,988,110,336 square millimeters

How to convert square miles to square millimeters

To convert square miles to square millimeters, multiply the number of square miles by 2,589,988,110,336. This factor is exact. To go the other way, multiply square millimeters by 3.861021585×10⁻¹³ (rounded).

square millimeters = square miles × 2,589,988,110,336

Example: 10 square miles = 25,899,881,103,360 square millimeters.

About these units

Square Mile (mi²)

US & ImperialCurrent unit

640 acres or about 2.59 km². Used for the area of cities, states and countries in the US and UK.

A thousand Roman paces, mille passus, became the mile, and under Elizabeth I Parliament fixed the statute mile at eight furlongs, or 5,280 feet, in place of the older Roman-based value. The square mile inherits that length. Its most famous use came in the United States: the Land Ordinance of 1785 started the Public Land Survey System so that western land could be surveyed and sold to pay war debts, beginning with the Seven Ranges in eastern Ohio.

In that system a section is roughly one square mile, or 640 acres, and a township is 36 sections in a square six miles on a side. One square mile is nearly 2.59 million square meters. Chicago's Midway International Airport, at about 650 acres, covers roughly 1.02 square miles. Beware the phrase mile square: a region 20 miles square has 400 square miles, but so does a rectangle 10 by 40 miles. The US survey version of the mile was retired from 1 January 2023, but the international square mile remains the unit for cities, states and countries in the US and UK.

1 square mile = 2,589,988.11 square meters (approximately).

Sources: Wikipedia: Square mile; Wikipedia: Public Land Survey System; Wikipedia: Mile

Square Millimeter (mm²)

Metric (SI)Current unit

A square one millimeter on a side. Used for the cross-section of wires and small parts.

Gauss gets the credit for putting the millimeter at the base of a scientific measuring system. His 1832 proposal for absolute units used the millimeter, milligram and second, although the centimeter-based CGS system later won out among scientists. The square millimeter is a one-thousandth-by-one-thousandth square of a meter, so it takes a million of them to make a square meter, and it has no famous inventor of its own.

Electricians know it best. Wire and cable sizes are given as the cross-sectional area of the copper conductor, and the standard sizes listed for UK domestic wiring are 1, 1.5, 2.5, 4, 6 and 10 mm². Twin and earth cable of 2.5 mm² typically serves sockets on a 16 A radial or 32 A ring circuit, 1 mm² serves lighting on a 6 A breaker, and 4 mm² feeds a cooker or shower. Conductor size depends on current capacity and allowed voltage drop, not on voltage alone. One square inch is exactly 645.16 mm², so small parts in either system compare easily.

1 square millimeter = 0.000001 square meters (exactly).

Sources: Wikipedia: Electrical wiring in the United Kingdom; Wikipedia: Centimetre-gram-second system of units; Wikipedia: Square metre

Related conversions

See all area units.