How many manhole covers are there?
Nobody counts manhole covers nationally, but the number follows from sewer network length because manholes are placed at fixed intervals by design standard — at every change of direction or gradient and at most 90 to 120 metres apart on straight runs. The United States has roughly 1.3 million km of public sewer, which puts the manhole count around 13 million before adding storm drains, water valves and utility vaults. New York City alone has several hundred thousand covers and gratings across its sewer, water, electrical and telecoms networks.
How the figure is arrived at
Sewer length divided by design spacing. The spacing figure is a real engineering standard rather than a guess, which makes this a better estimate than it sounds, but the answer only covers sanitary sewer manholes — including storm, electrical and telecoms access covers could double or triple it.
How confident it is
- Low estimate
- 8,000,000
- High estimate
- 20,000,000
- Spread
- 2.5× between the bounds
Other things people built counts
- How many countries are there in the world? 195 — or 193, or 206, or 249, depending on who is counting
- How many cars are there in the world? about 1.5 billion motor vehicles
- How many planes are in the air right now? roughly 10,000 to 20,000 at any moment
- How many languages are there in the world? about 7,150 living languages
- How many McDonald's are there? about 43,000 in over 100 countries
- How many phones are there in the world? about 8.9 billion mobile connections — more than there are people
- How many nuclear weapons are there? about 12,200 warheads
- How many websites are there? about 1.1 billion hostnames — but only around 200 million active
- How many books have ever been published? about 130 million as of 2010 — probably over 200 million now
- How many airports are there in the world? about 45,000 with runways — but only around 4,000 with scheduled airline service
- How many ATMs are there in the world? about 3 million
- How many cities are there in the world? about 10,000 with over 50,000 people; 33 megacities over 10 million
- How many buildings are there in the world? somewhere between 1.5 and 4 billion
- How many computers are there in the world? roughly 2 billion personal computers in use
Common questions
- How many manhole covers are there?
- roughly 13 million in the United States, on a rough estimate
- How is that estimated?
- Sewer length divided by design spacing. The spacing figure is a real engineering standard rather than a guess, which makes this a better estimate than it sounds, but the answer only covers sanitary sewer manholes — including storm, electrical and telecoms access covers could double or triple it.
Related pages
- How many countries are there in the world? 195 — or 193, or 206, or 249, depending on who is counting
- How many cars are there in the world? about 1.5 billion motor vehicles
- How many planes are in the air right now? roughly 10,000 to 20,000 at any moment
- How many languages are there in the world? about 7,150 living languages
- How many McDonald's are there? about 43,000 in over 100 countries
- How many phones are there in the world? about 8.9 billion mobile connections — more than there are people
- How many nuclear weapons are there? about 12,200 warheads
- How many websites are there? about 1.1 billion hostnames — but only around 200 million active
- How many people are there in the world? Living things and the natural world
- How many stars are there in the universe? Space and the universe
- How many bones are in the human body? The human body
- How many grains of sand are there on Earth? Living things and the natural world
- How many ants are there in the world? Living things and the natural world
- How many trees are there in the world? Living things and the natural world
Sources
- Calculated on this page — At One Place