Where do RealSize.World numbers come from?

Three different concepts, three separate metrics

US states

Areas of the 50 states and Washington, DC come from the Census Bureau table for boundaries as of January 1, 2010. Comparisons use land plus inland water (lakes, rivers), as the area statistics of most countries do, and that is also what the outline on the map shows. The Census total area adds coastal and territorial water and part of the Great Lakes. It is shown beside the first figure, and a state set beside the whole USA uses it, because that is how the USA figure is measured. For example, Michigan has 151,617 km² of land and inland water, and 250,487 km² with its Great Lakes water.

U.S. Census Bureau · State Area Measurements and Internal Point Coordinates ↗

USA comparisons include all 50 states and Washington, DC, including Alaska and Hawaii. Lower 48 means the 48 contiguous states and is not used as a substitute for the whole USA.

England, Scotland, Wales and Northern Ireland

Areas of the four nations of the United Kingdom come from ONS (Standard Area Measurements, December 2024). We use the area to the mean high water line, including inland water. Together they come to 244,378 km², which matches the figure for the whole United Kingdom in our data.

• England: 130,464 km² (land 130,313 km²).
• Scotland: 78,801 km² (land 77,900 km²).
• Wales: 20,783 km² (land 20,737 km²).
• Northern Ireland: 14,330 km² (land 13,793 km²).

Source: Office for National Statistics licensed under the Open Government Licence v.3.0. Contains OS data © Crown copyright and database right 2025.

ONS · Standard Area Measurements for the Countries (December 2024) ↗ · ONS geography licences ↗

Outlines and boundaries

Outlines come from Natural Earth through world-atlas. The app uses 1:50m and 1:110m scales, so geometry is simplified for visualization and is not suitable for geodetic measurement. Natural Earth displays de facto boundaries by default. Names and boundaries do not express a RealSize.World position on territorial disputes.

New outlines of states, UK nations and Europe use Natural Earth 5.1.1 directly at 1:50m scale. The Great Lakes are cut out of the states that border them, while other lakes stay inside the outline. Alaska includes the Aleutians on both sides of 180° longitude. France comparisons cover metropolitan France and Corsica, excluding overseas territories. Europe includes European Russia, Great Britain, Ireland and Iceland. Its approximate 10,180,000 km² area is an editorial continental estimate, not the area of the European Union. The conventional division between Europe and Asia follows Natural Earth's physical regions layer.

Natural Earth releases its data in the public domain and permits modification and commercial use. State figures are attributed to the Census Bureau and the figures for England, Scotland, Wales and Northern Ireland to ONS. We do not reproduce their photographs or graphic material.

Natural Earth · terms of use ↗ · Census Bureau · data citation ↗ · Geographic file provenance and versions ↗

Antipodes and the Earth's interior

The “Dig through the Earth” tool checks whether an antipode falls on land using the Natural Earth 1:50m map. To find the nearest land it adds small islands from the 1:10m map (world-atlas 2.0.2) that the 1:50m map lacks, with about a dozen outline points per island. Ocean and sea names come from the water areas used in the quizzes. Distances follow great circles on a sphere with a radius of 6,371 km and are rounded to 10 km.

We calculate the fall time, speed and pressure ourselves from the PREM density model (A. M. Dziewonski, D. L. Anderson, Preliminary Reference Earth Model, Physics of the Earth and Planetary Interiors 25, 1981): gravity from the mass inside each shell, pressure from the weight of the rock above and the motion of a body falling without air resistance. The model reproduces the Earth's mass, surface gravity and central pressure, and the fall time matches the paper by A. R. Klotz (American Journal of Physics 83, 2015). Tunnel length and the plumb-line offset use the WGS 84 ellipsoid. We do not give interior temperatures as numbers. The approximate starting point comes from the device time zone: the coordinates of each zone's principal city come from the IANA time zone database, release 2025b (zone.tab, zone1970.tab and backward, public domain).

A. R. Klotz · The Gravity Tunnel in a Non-Uniform Earth ↗

Rivers

River lengths follow the Encyclopædia Britannica table of the longest rivers, measured to the most distant source. The USGS gives the same figures for the Nile, the Amazon and the Yangtze, and the US National Park Service for the Mississippi-Missouri. For rivers with a disputed length, such as the Amazon, we give the main value and the range of measurements. Mean discharge at the mouth comes from the table of the 50 largest rivers by A. Dai and K. E. Trenberth (Journal of Hydrometeorology, 2002), and for rivers outside that table from the source named on the river's page. The numbers are facts, described in our own words with their source.

River lines come from the Natural Earth 5.1.1 rivers and lake centerlines layer at 1:10 million (public domain). We choose each river's main stem by hand, from the mouth to the most distant source, and simplify it to about 2 km. At this scale the line is 5 to 35 percent shorter than the river, because it skips small bends and estuaries, so it is never used to state a length. The Mercator factor is the mean of 1/cos(latitude) along that line: how many times longer the river looks on a Mercator map at the scale of the equator. When we move a river onto another country, we rotate it over the globe without changing its shape or length, just like country outlines on the projection maps.

Encyclopædia Britannica · World's longest rivers · Dai, Trenberth 2002 · Natural Earth 5.1.1

Data licences and citation

We use data from external sources under their licences. Citations follow the format requested by each data provider.

• The World Bank: World Development Indicators: Population, total (SP.POP.TOTL). Data source: UN Population Division, national statistical offices, Eurostat, UN Statistics Division. Licence: CC BY 4.0 ↗
• The World Bank: World Development Indicators: Land area (AG.LND.TOTL.K2), Surface area (AG.SRF.TOTL.K2). Data source: Food and Agriculture Organization of the United Nations (FAO). Licence: CC BY 4.0 ↗
• United Nations Statistics Division: Demographic Yearbook 2024, Table 3 (total surface area).
• Monaco — a single territorial-area fact: 208.4 ha, converted by us to 2.084 km². Source: IMSEE / Direction de la Prospective, de l’Urbanisme et de la Mobilité, Monaco en chiffres, 2023 edition, p. 16. This edition's value does not include later territorial extensions. We do not reproduce the publication's tables, text or maps. Monaco en chiffres 2023 ↗ · Source terms ↗
• Historical empire borders: Cliopatria (Seshat Global History Databank) ↗, modified: fitted to the coastline and simplified. Licence: CC BY 4.0 ↗
• Historical context of the empires: Smithsonian National Museum of the American Indian, official history of Toruń, official history of Bydgoszcz. We describe only historical facts in our own words; we do not reuse their texts, photographs or maps.
• Flags: Flagpedia.net ↗, public domain. We downloaded the files once and serve them from our own server.

Our changes: within the retrieved World Bank snapshot, we use the latest available year for each metric. We calculate population density ourselves as population divided by land area and round the result. When the UN gives no total surface area, or gives a value smaller than the land area, we use the World Bank total surface area instead. Monaco is the exception: we pinned the IMSEE edition described above; this correction was verified on October 13, 2026. Rankings, comparisons and quizzes are calculated from these data. The data providers are not responsible for these changes and do not endorse RealSize.World.

How calculations and comparisons work

• Size comparisons use total surface area, not area calculated from simplified SVG geometry.
• The 1:1 overlay uses a locally centered azimuthal equal-area projection at a shared scale. It preserves geometric area ratios, which need not equal statistical total-area ratios: coastal outlines omit some waters and are simplified.
• The Mercator verdict is an estimate using 1/cos²(φ) at each outline's centroid latitude. It does not measure the entire projected area.
• Population density is calculated as population divided by land area when both metrics are available.
• Population and area reference periods may differ; they are displayed separately.
• A missing observation is not replaced with zero or an average.

Current snapshot coverage

Updates and quality control

Data is fetched by a controlled importer during editorial updates, stored in the repository, and validated before publication. The site does not fetch numbers live on every visit. This makes builds reproducible and prevents an external API outage from changing page content.

The importer stops on an invalid source response. Validation checks codes, values, sources, and the relationship between total and land area. Exceptional cases are flagged for a manual decision.