9,650 t21,300,000 lb
The air in an imaginary cylinder just big enough to hold the Eiffel Tower weighs about 9,650 tonnes (21.3 million lb), more than the tower’s 7,300 tonnes of iron. That is our calculation: a cylinder 177 m (581 ft) across and 330 m (1,083 ft) tall holds about 8.1 million m³ of air, at roughly 1.2 kg per cubic metre.
| Cylinder of air on a freezing day0 °C (32 °F) at the ground | 10,300 t22,700,000 lb |
|---|---|
| Cylinder of air on a standard day15 °C (59 °F), standard sea-level air | 9,770 t21,500,000 lb |
| Cylinder of air on a mild dayThe figure on this page, about 18 °C (64 °F) | 9,650 t21,300,000 lb |
| Cylinder of air on a hot day35 °C (95 °F) at the ground | 9,150 t20,200,000 lb |
| The tower’s iron, for comparisonOfficial figure for the metal structure | 7,300 t16,100,000 lb |
| Air in a box around the tower324 × 125 × 125 m | 6,200 t13,700,000 lb |
Nobody has weighed this air; it is a calculation. The Eiffel Tower stands on a square base 125 m (410 ft) on each side and is 330 m (1,083 ft) tall to the tip of its antennas. The narrowest upright cylinder that fits around that square has to be as wide as the square’s diagonal, about 177 m (581 ft). Its floor covers about 24,500 m², and at 330 m tall it holds about 8.1 million cubic metres of air. The tower’s own iron fills only a tiny part of that space, so we leave it out.
At sea level, standard air at 15 °C weighs 1.225 kg per cubic metre. Air thins as you go up, so we used NASA’s standard atmosphere model, which lowers the pressure with height; at the top of the tower the air is about 3% lighter than at the bottom. On a standard 15 °C day, the cylinder holds about 9,770 tonnes of air, and on a 20 °C day about 9,600 tonnes. The 9,650 tonnes on this page is a mild day of about 18 °C.
Cold air is denser than warm air. By the same model, a cubic metre of air at ground level weighs about 1.29 kg at 0 °C and about 1.16 kg at 30 °C. So on a freezing winter day the cylinder holds about 10,300 tonnes of air, and on a 35 °C heatwave day about 9,150 tonnes, a swing of more than 1,100 tonnes.
Humidity pulls the other way from what you might expect. Water vapour molecules are lighter than the nitrogen and oxygen they replace (18 g per mole against about 29 g for dry air), so humid air weighs slightly less than dry air at the same temperature and pressure.
That makes for a close race with the tower itself. The iron structure weighs 7,300 tonnes, and the whole tower with its lifts, floors, shops and antennas about 10,100 tonnes. On a warm day the complete tower is heavier than the air in its cylinder; on a freezing day the air wins.
The shape matters. A rectangular box that just fits the tower, 324 m by 125 m by 125 m, holds about 5.1 million m³, and Wikipedia’s Eiffel Tower article puts the air in it at about 6,200 tonnes, almost as much as the iron.
A cylinder has to be wider than the base to fit its corners, so its floor is about 1.57 times the area of the square (π ÷ 2). That is why the cylinder holds about 9,650 tonnes and the box only about 6,200.
About 1.2 kg per cubic metre near sea level, or 1.2 g per litre. Standard sea-level air at 15 °C weighs 1.225 kg per cubic metre; colder air is heavier and warmer air lighter.
The air in a cylinder just big enough to hold the tower, about 9,650 tonnes on a mild day, weighs more than the tower’s 7,300 tonnes of iron. It weighs a little less than the whole tower with all its fittings, about 10,100 tonnes, except on days near freezing.
About 177 m (581 ft) across, the diagonal of the tower’s 125 m square base, and 330 m (1,083 ft) tall. That is about 8.1 million cubic metres.
Yes. At the same pressure, a cubic metre of air weighs about 1.29 kg at 0 °C and about 1.16 kg at 30 °C, roughly 10% less. Over the Eiffel Tower’s cylinder that is a difference of about 1,000 tonnes.
Last checked October 4, 2026.
