Exactly how every number on this site is calculated.
1. Baseline population. Each city starts from a baseline population figure taken from the SimpleMaps World Cities Database (baseline date: 2026-05-20).
2. Demographic rates. Every country is assigned an annual crude birth rate, crude death rate and life expectancy from UN World Population Prospects and World Bank Open Data. These are national averages applied to each city in that country.
3. Live counters. Births per second = (population × birth rate ÷ 1,000) ÷ 365.25 ÷ 24 ÷ 60 ÷ 60. Deaths per second use the same formula with the death rate. The live population = baseline + cumulative births − cumulative deaths since the baseline date.
4. Scenario calculations. Any future natural-change scenario compounds the current birth-minus-death rate. It is not an official forecast and does not model migration, boundary changes, policy, economics or changing demographic rates.
5. Distances. All distances use the Haversine formula (great-circle, straight-line) from latitude/longitude coordinates. Road distances are typically longer.
6. Limitations. City-level rates are approximations of national averages. Live counters are statistical estimates, not live vital-registration. Figures may differ from official census results. These limitations are disclosed on every city, country and world page.
7. Update cadence. Counters are recalculated from the stored baseline on each request. The sitemap last-modified date changes only when the underlying dataset/model is materially re-imported, not merely because a counter ticked.