Square kilometre (International spelling as used by the International Bureau of Weights and Measures) or square kilometer (American spelling), symbol km2, is a decimal multiple of the SI unit of surface area, the square metre (or square meter), one of the SI derived units. 1 km2 is equal to:
It is also approximately equal to:
- 1 m2 = 0.000001 (10−6) km2
- 1 hectare = 0.01 (10−2) km2
- 1 square mile = 2.5899km2 
- 1 acre = about 0.004047km2, 0.4047ha or 4047 m2 
Note: "km2" means (km)2, square kilometre or kilometre squared and not k(m2), kilo–square metre. For example, 3 km2 is equal to 3×(1,000m)2 = 3,000,000 m2, not 3,000 m2.
Note also that if a piece of land, say a large park, is described as five kilometres square, that means it has the shape of a square, each side of the square being five kilometres long. This means that the park has an area of twenty-five square kilometres (and not five square kilometres).
Examples of areas of 1 square kilometre
Topographical Map grids
Topographical map grids are worked out in metres, with the grid lines being 1,000 metres apart.
- 1:100,000 maps are divided into squares representing 1 km2, each square on the map being one square centimetre in area and representing 1 km2 on the surface of the earth.
- For 1:50,000 maps, the grid lines are 2 cm apart. Each square on the map is 2 cm by 2 cm (4 cm2) and represents 1 km2 on the surface of the earth.
- For 1:25,000 maps, the grid lines are 4 cm apart. Each square on the map is 4 cm by 4 cm (16 cm2) and represents 1 km2 on the surface of the earth.
In each case, the grid lines enclose one square kilometre.
Medieval city centres
The area enclosed by the walls of many European medieval cities were about one square kilometre. These walls are often either still standing or the route they followed is still clearly visible, such as in Brussels, where the wall has been replaced by a ring road, or in Frankfurt, where the wall has been replaced by gardens. The approximate area of the old walled cities can often be worked out by fitting the course of the wall to a rectangle or an oval (ellipse). Examples include
- Delft, Netherlands (See map alongside)
- The walled city of Delft was approximately rectangular.
- Lucca (Italy)
- The medieval city is roughly rectangular with rounded north-east and north-west corners.
- Brugge (Belgium)
- The medieval city of Brugge, a major centre in Flanders, was roughly oval or ellipsoidal in shape with the longer or semi-major axis running north and south.
- Chester United Kingdom
- Chester is one of the smaller English cities that has a near-intact city wall.
Parks come in all sizes; a few are almost exactly one square kilometre in area. Here are some examples:
- Riverside Country Park, UK.
- Brierley Forest Park, UK.
- Rio de Los Angeles State Park, California, USA 
- Jones County Central Park, Iowa, USA.
- Kiest Park, Dallas, Texas, USA 
- Hole-in-the-Wall Park & Campground, Grand Manan Island, Bay of Fundy, New Brunswick, Canada 
- Downing Provincial Park, British Columbia, Canada 
- Citadel Park, Poznan, Poland 
- Sydney Olympic Park, Sydney, Australia, contains 1 square kilometre of wetlands and waterways.
Using the figures published by golf course architects Crafter and Mogford, a course should have a fairway width of 120 metres and 40 metres clear beyond the hole. Assuming a 6,000 metres (6,600 yd) 18-hole course, an area of 80 hectares (0.8 square kilometre) needs to be allocated for the course itself.[Note 1] Examples of golf courses that are about one square kilometre include:
- Manchester Golf Club, UK 
- Northop Country Park, Wales, UK 
- The Trophy Club, Lebanon, Indiana, US 
- Qingdao International Country Golf Course, Qingdao, Shandong, China 
- Arabian Ranches Golf Club, Dubai 
- Sharm el Sheikh Golf Courses: Sharm el Sheikh, South Sinai, Egypt 
- Belmont Golf Club, Lake Macquarie, NSW, Australia 
Other areas of one square kilometre or thereabouts
- The Old City of Jerusalem is almost 1 square kilometre in area.
- Milton Science Park, Oxfordshire, UK.
- Mielec Industrial Park, Mielec, Poland 
- The Guildford Campus of Guildford Grammar School, South Guildford, Western Australia
- Sardar Vallabhbhai National Institute of Technology (SVNIT), Surat, India 
- Île aux Cerfs Island, near the east coast of Mauritius.
- Assume that each hole requires (6000÷18 + 40) = 373 metres in length. The area needed is (18 × 373 × 120 ÷ 10,000) = 80.64 ha (1 hectare = 10,000 square metres).
- Conversion of units
- SI prefix for the precise meaning of the prefix "k"
- Square Kilometre Array, a proposed radio telescope in South Africa or Australia, which is intended to have a collecting area of approximately 1 km2
- There are 0.386102159 international square miles in a square kilometer while there are 0.386100614 US Survey square miles in the same measure. This is because the US Survey measures are very slightly larger than the international measures. "UnitConversion.org Area Converter". web page. UnitConversion.org. 2009. Retrieved 4 July 2012.
- There are 247.105381467 international acres in a square kilometre while there are only 247.104393047 of the very slightly larger US Survey acres. "UnitConversion.org Area Converter". web page. UnitConversion.org. 2009. Retrieved 4 July 2012.
- An International square mile equals 2.58998811|km2 while the slightly larger US Survey square mile equals 2.58999847|km2. "UnitConversion.org Area Converter". web page. UnitConversion.org. 2009. Retrieved 4 July 2012.
- 1 acre (International) = 0.004046856km2, 0.4046856ha or 4046.856m2 while 1 acre (US Survey) = 0.004046873km2, 0.4046873ha or 4046.873m2 "UnitConversion.org Area Converter". web page. UnitConversion.org. 2009. Retrieved 13 June 2012.
- Measurements taken from Google Earth
- Howe, Steve. "Chester: A Virtual Stroll around the Walls". Retrieved 7 October 2012.
- "Medway Council Riverside Country Park". web page. Medway Council. 2012. Retrieved 9 June 2012.
- "Ashfield Brierley Forest Park". web page. Ashfield District Council. 2012. Retrieved 9 June 2012.
- "California Department of Parks and Recreation Rio de Los Angeles State Park". web page. State of California. 2012. Retrieved 9 June 2012.
- "Parks & Recreation Central Park, Center Junction, Iowa". web page. Jones County Tourism Association. Retrieved 9 June 2012.
- "A History of Kiest Park". web page. Friends of Oak Cliff Parks. 2010. Retrieved 9 June 2012.
- "Hole-in-the-Wall Park & Campground". web page. Hole-in-the-Wall Park & Campground. 2012. Retrieved 9 June 2012.
- "BC Parks Downing Provincial Park". web page. British Columbia Ministry of Environment. Retrieved 9 June 2012.
- "Citadel Park". web page. Poland Travel. Retrieved 9 June 2012.
- "Sydney Olympic Park Parklands Fact Sheet". web page. Sydney Olympic Park Authority. Retrieved 9 June 2012.
- "Golf Course Safety". Crafter + Mogford, golf course architects. Retrieved 5 October 2012.
- "Visitor Information [Manchester Golf Club]". web page. Manchester Golf Club Ltd. Retrieved 11 June 2012.
- "Welcome to the Trophy Club". web page. The Trophy Club. Retrieved 11 June 2012.
- "travelchinaguide.com Related golf club information". web page. TravelChinaGuide.com. Retrieved 11 June 2012.
- "7 Days in Dubai Arabian Ranches Golf Club". web page. Catchpole Communications FZ-LLC, Al Sidra Media LLC. Retrieved 11 June 2012.
- "Sharm el Sheikh Golf Courses: Sharm el Sheikh, South Sinai, Egypt". web page. TravelSmart Ltd: World Guides. Retrieved 11 June 2012.
- "Belmont Golf Club, Lake Macquarie, History". web page. Belmont Golf Club. Retrieved 11 June 2012.
- "Jerusalem - The Old City". web page. The American-Israeli Cooperative Enterprise. 2012. Retrieved 6 July 2012. Actually, about 89 hectares.
- "Science Vale UK". web page. Abbey House. Retrieved 7 July 2012.
- "Invest in Poland". web page. Polish information and foreign investment agency. Retrieved 7 July 2012.
- "Guildford Grammar". web page. Waterhall Private Estate. Retrieved 6 July 2012.
- "39th National Conference on Fluid Mechanics and Fluid Power". web page. Department of Mechanical Engineering, Sardar Vallabhbhai National Institute of Technology (SVNIT). Retrieved 7 July 2012.
- "MauritiusAttraction". Amity Institute of Higher Education, Mauritius. Amity Institute of Higher Education. 2011. Retrieved 27 June 2013.