Square Kilometre
The square kilometre (symbol: km²) is a metric unit used to measure area or surface area. As a multiple of the square metre, it serves as a standard for measuring larger geographic regions, city centers, and land parcels. In American English, it is spelled as "square kilometer."
To understand the scale of a square kilometre, it is helpful to visualize a square where each side is exactly 1,000 metres (1 kilometre) long. Because area is calculated by multiplying length by width, the total area is 1,000 m × 1,000 m, resulting in 1,000,000 square metres.
Key Facts
- SI Unit: It is a derived unit of the International System of Units (SI).
- Exact Value: 1 km² equals exactly 1,000,000 square metres (m²).
- Hectare Relation: 1 km² is equivalent to 100 hectares (ha).
- Imperial Approximation: 1 km² is approximately 0.3861 square miles or 247.1 acres.
- Notation: The symbol km² represents a square kilometre, not a "kilo-square metre."
Unit Conversions
Converting between the metric and imperial systems is essential for global geographic data. The following table provides the precise and approximate conversions for the square kilometre.
| From 1 km² To... | Equivalent Value |
|---|---|
| Square Metres (m²) | 1,000,000 |
| Hectares (ha) | 100 |
| Square Miles (mi²) | ~0.3861 |
| Acres | ~247.1 |
Conversely, if you are converting from other units into square kilometres, 1 square mile is approximately 2.5899 km², and 1 acre is roughly 0.004047 km².
Visualizing the Square Kilometre
Topographical Map Grids
Topographical maps frequently use grids to help users determine location and area. These grids are typically based on 1,000-metre intervals, meaning each grid square represents 1 km² on the Earth's surface. Depending on the map scale, the physical size of these squares on paper varies:
- 1:100,000 scale: Each 1 km² square is 1 cm × 1 cm.
- 1:50,000 scale: Each 1 km² square is 2 cm × 2 cm.
- 1:25,000 scale: Each 1 km² square is 4 cm × 4 cm.
Medieval City Centres
Many historic European city centres were originally enclosed by walls that spanned an area of roughly one square kilometre. While many of these walls have been replaced by ring roads or gardens, their footprints remain visible.
- Delft, Netherlands: The walled city was approximately rectangular (1.30 km by 0.75 km), totaling about 0.9 km².
- Lucca, Italy: A roughly rectangular city with a maximum east-west distance of 1.36 km and north-south of 0.80 km, totaling approximately 1.088 km².
- Chester, UK: A smaller example where the area within the near-intact walls is approximately 0.504 km².
- Bruges, Belgium: A larger elliptical city with a semi-major axis of 2.53 km and semi-minor axis of 1.81 km, totaling about 3.597 km².
Parks and Recreation
Various public spaces and sports facilities align closely with the 1 km² measurement. Examples of parks near this size include Riverside Country Park (UK), Brierley Forest Park (UK), and Rio de Los Angeles State Park (USA). In contrast, larger areas like the Sydney Olympic Park contain 6.63 km² of waterways and wetlands.
Golf courses also provide a practical example. Based on architectural standards for fairway width and hole length, a standard 18-hole course (6,000 metres) requires approximately 80 hectares, or 0.8 km². Courses such as the Manchester Golf Club (UK) and Arabian Ranches Golf Club (Dubai) are approximately one square kilometre in size.
Other Notable Areas
Several other global landmarks and institutions occupy roughly 1 km², including the Old City of Jerusalem, the Mielec Industrial Park in Poland, and Peng Chau Island in Hong Kong.
Frequently Asked Questions
What is the difference between a square kilometre and a kilo-square metre?
The term square kilometre (km²) refers to a square that is 1,000 metres by 1,000 metres, totaling 1,000,000 m². A "kilo-square metre" would imply 1,000 times a single square metre (1,000 m²), which is a significantly smaller area.
How many hectares are in one square kilometre?
There are exactly 100 hectares in one square kilometre.
How does a square kilometre compare to a square mile?
A square kilometre is smaller than a square mile. One square kilometre is approximately 0.3861 square miles, while one square mile is approximately 2.5899 square kilometres.
Why do topographical maps use 1 km² grids?
Grid lines spaced at 1,000-metre intervals provide a consistent and easy-to-calculate method for measuring distance and area on the ground, regardless of the map's overall scale.