How Big is a Redwood Tree
When speaking of Redwood tree sizes, one should distinguish between the two types. 
The Coast Redwood trees (Sequoia sempervirens) are the tallest on Earth (the highest reaches up to 379 ft). The Giant Sequoia or Sierra Redwood trees (Sequoiadendron giganeum) reach 290 ft (average) and have the biggest volume.
The Coast Redwood Trees
The Coast Redwood trees can be found off the coast of California (hence the moniker California Redwood). Specifically they are found along the California coast along the southwest corner of Oregon. It extends 150 miles south to San Francisco at the Big Sur.
The tree grows very fast. After 20 years the tree can reach heights of 50 ft. Its diameter by then will reach 8 inches. The average Redwood tree size is 200 to 240 ft. The diameter will reach 10 to 15 ft.
But as noted earlier, some variants reach heights of over 350 ft. Those over 350 ft will have a diameter of over 20 ft. These trees can live for over 2,000 years.
On the average, the bark is 12 inches thick. The land occupied by the Coast Redwoods is over 750 km. The tallest tree is Hyperion (in Redwood National Park) at 379.1 ft. Currently there are over 30 trees over 360 ft tall. There are over 150 trees over 350 ft tall.
There are unconfirmed reports of a 380 ft tree that was chopped down in 1912. The biggest Redwood tree size possible is 425 ft. In terms of volume, the biggest is the Lost Monarch. It is 320 ft high with a diameter of 26 ft. Its total volume is 42,500 cubic ft.
Other Coast Redwood Giants
These include the Del Norte Titan (306 ft), the Fusion Giant (348 ft). the El Viejo del Norte (323 ft) and the Howland Hill Giant (330 ft).
The Giant Sequoias
In terms of volume, the Giant Sequoias are the largest on the planet. The average height is 290 ft. The diameter average is 25 ft. Some trees reach up to 311 ft. In terms of diameter, some reach 57 ft.
In terms of age, the oldest known is 3,500 years old. The bark can be 3 ft thick. The leaves are 5 mm. It is found in Sierra Nevada, California but has been cultivated in various parts of the world. One of the biggest ones is in Scotland, reaching 177 ft.
Measurement of Giant Sequoia Redwood tree sizes are based on height, girth at the ground and the volume. The tree called General Sherman has the biggest volume at 52,508 cubic ft. The tallest reaches a height of 311 ft (unnamed).
The oldest are 3,500 years old and found in the Converse basin. The biggest girth belongs to the Waterfall tree at 155 ft in Alder Creek Grove.
The Waterfall tree also has the biggest base diameter (57 ft). The biggest diameter at the breast is General Grant (29 ft). The largest limb is the Arm Tree with a diameter of 12.8 ft. The thickest bark measures 3 ft.
As astonishing as the Redwood tree sizes are, there may be more still waiting to be discovered. Hyperion was seen in 2006 and many more could still be hidden.
