Square Meter to Square Kilometer

Average new apartment sizes vary dramatically: Hong Kong averages about 40 m², Tokyo 63 m², London 72 m², the US 91 m², and Australia 137 m². New York City studio apartments average around 45 m². The smallest habitable apartments in Hong Kong ("nano flats") have been as small as 12 m² — including kitchen, bathroom, and sleeping area.

Typical monocrystalline silicon panels achieve 180–220 W/m² under standard test conditions (1,000 W/m² solar irradiance). Premium panels exceed 220 W/m². In practice, real-world output is 15–25% lower due to heat, shading, and angle. A south-facing UK rooftop receives roughly 1,000–1,100 kWh/m²/year of solar energy; at 20% efficiency, that is 200–220 kWh/m²/year of electricity generated.

A standard FIFA football pitch is 7,140 m² (105 × 68 m, though ranges are permitted). An Olympic swimming pool is 1,250 m² (50 × 25 m). A tennis court is 260 m² (23.77 × 10.97 m). A basketball court is 420 m². A boxing ring is 36–37 m². At the tiny end, a table tennis table is just 4.18 m² (2.74 × 1.525 m).

Price per m² normalizes for size and allows direct comparison between differently sized properties. Monaco has the highest residential property prices at roughly €50,000/m². Prime London locations run £15,000–30,000/m². This metric also reveals when a small "luxury" flat is priced disproportionately — a 25 m² London studio at £500,000 works out to £20,000/m², more expensive per m² than many large houses.

A typical lawn produces 150–300 g of clippings per m² per mowing cycle. Grass grows at roughly 2–6 cm/week in growing season. Lawn fertiliser is applied at rates of 15–35 g/m² of nitrogen per application. A 100 m² garden lawn requires about 150–200 liters of water per week during dry summer periods — a useful calculation for water restrictions.

Vatican City is the smallest sovereign state at just 0.44 km². Monaco is 2.02 km², San Marino 61 km². For comparison, Liechtenstein is 160 km² and Luxembourg 2,586 km². The world's largest country, Russia, covers 17,098,242 km² — nearly 39 million times the area of Vatican City. Russia spans 11 time zones and contains 13% of the world's land area.

Global deforestation removes approximately 50,000–100,000 km² of forest per year. Brazil lost roughly 11,568 km² of Amazon rainforest in 2022 alone. For scale, that is an area larger than Jamaica disappearing every year. At peak deforestation rates in the 1990s, Brazil was losing 29,000 km²/year. Satellite monitoring (PRODES, Global Forest Watch) now tracks loss in near real-time at 30 m resolution.

Population density (people per km²) is a key demographic statistic. Monaco is the most densely populated state at about 26,000 people/km². Bangladesh is the most populous large country at ~1,300/km². Australia averages 3.5/km². Mongolia is the least dense large country at 2/km². For cities, Manila reaches over 100,000/km² in its densest districts, making it one of the most densely populated urban areas on Earth.

Estimates range from 700,000 km² to 1,600,000 km² — larger than France to twice the size of Texas. However, the "patch" is misleading: it is not a solid island but a high-concentration zone of microplastic particles dispersed through the upper water column. Cleanup is extremely difficult because the particles are spread over such an enormous area at low density per m².

Major wildfires are tracked in km² or, in the US, in acres. The 2019–2020 Australian Black Summer fires burned approximately 186,000 km² — an area larger than Syria. The 2021 Dixie Fire in California burned 1,900 km², the largest single fire in California history. The 2023 Canadian wildfires burned a record 180,000+ km² of forest, releasing more CO₂ than Canada's annual human emissions.