The Council on Tall Buildings and Urban Habitat (CTBUH) is the group that decides what counts as a tall building and which one is the world's tallest. It wrote the international standards for measuring and defining tall buildings; it is recognized as the arbiter for the title World's Tallest Building. There is no absolute definition of a tall building. The CTBUH calls the idea subjective; it says the number of floors is a poor guide, because floor heights differ. As a typical threshold, a building of 14 or more stories, or more than 50 meters (165 feet), could count as tall.

The CTBUH measures a building's height from the lowest main open-air entrance used by people on foot. It keeps three separate records; one is height to the architectural top. One is height to the highest occupied floor; one is height to the tip, which is the highest point of anything on the building. As skyscrapers grew taller, wind became a new enemy for engineers. The PBS Building Big site says that today's tallest skyscrapers, almost 1,500 feet tall, must be 50 times stronger against wind than the typical 200-foot buildings of the 1940s.

Engineers describe the forces on a building with a few words. Compression squeezes a material together and shortens it. Tension stretches a material apart and lengthens it. The lower columns of a skyscraper are in compression because of the weight above them. The Home Insurance Building in Chicago, finished in 1885, is often called the first skyscraper. It was ten stories and 42.1 meters (138 feet) tall. Two floors were added in 1891, so it reached 54.9 meters (180 feet). It was torn down in 1931. The word skyscraper came into use in the 1880s, after the first tall steel-frame buildings went up in American cities.

Elevators set the speed limit for tall buildings. Taipei 101 once had the fastest elevators in the world. They carried riders from the 5th floor to the 89th floor in 37 seconds. Safe elevators were what first made tall buildings practical. The Great Pyramid of Giza stood 146.6 meters (481 feet) tall when it was new. It was the tallest human-made structure for more than 3,700 years. Most of its smooth limestone casing was later removed, so it is now 138.5 meters (454.4 feet) tall.

Builders made the Great Pyramid from an estimated 2.3 million large blocks that weighed about 6 million tonnes in all. It was built around 2600 BC over about 26 years as a tomb for the Egyptian king Khufu. As of November 2026, the Burj Khalifa in Dubai is the tallest building in the world, at 828 meters. The CTBUH measures it from the lowest entrance up; the Eiffel Tower and the Great Pyramid each held the title of tallest structure in the world for a time.

Words to know

• arbiter: final judge
• compression: squeezing
• tension: stretching force
• threshold: starting point