You can not simply change from a measurement of volume to that of mass, for example if you had a 1m x 1m x 1m cube and filled it with lead, it would have a greater mass than if it were filled with air or wood.
As such, in order to find the mass of an object of a given volume you are required to know what material the object is composed of, and hence it's density. Then it's mass can be calculated as below:
Mass = Density x Volume
29mt
An Apatasaurus was 20 feet tall and weighed 30 tons.
20 tons. and they are 130 feet tall.
4000
Sixteen Tons
The megatherium was 20 to 25 ft tall and weighted 8 tons
18 tonnes (metric tons, same as 1000 kilograms) are 39683 pounds.
around 20 tons with the blade
There are 40,000 pounds in 20 tons.
A nuclear explosive device can be any size at all. The smallest are roughly 5 inches in diameter and a foot long, the largest built was the Ivy Mike "Sausage" device in 1952, which was 20 feet in diameter and 80 feet tall weighing 82 tons. Ivy Mike also needed roughly another 100 tons of cryogenic refrigeration equipment to keep its liquid deuterium/tritium fuel cold.
Over 200 feet tall, and weighing over 80 tons.
between 3" - 3 3/4" in diameter