Tardigrade (Water bear)
0.25 mm
Adult body length
A chubby eight-legged micro-animal that can survive drying out, seen from the side. About 0.25 mm long.
Published
How big is that?
0.25 mm is 3.6 times the width of a human hair and 3.5% of a grain of rice.
Tardigrade is the 12th smallest of the 32 Tiny Worlds objects, and the 12th smallest of the 172 objects across all five SizeItUp games.
Size comparison
To scale, smallest to largest: Tardigrade in orange beside the Tiny Worlds objects nearest in size, in teal.
| Object | Size | vs Tardigrade |
|---|---|---|
| Human egg cellThe largest cell in the human body, at ovulation. | 0.115 mm across | 46% of the size |
| Paramecium (P. caudatum)A slipper-shaped single cell that swims with thousands of tiny hairs. | 0.225 mm long | 90% of the size |
| Tardigrade (Water bear) | 0.25 mm long | – |
| Grain of sand (Medium)A grain of medium sand, as geologists grade it. | 0.375 mm across | 1.5× bigger |
| Spider mite (Two-spotted, female)A sap-sucking mite that spins fine webs on houseplants, seen from above. | 0.4 mm long | 1.6× bigger |
In other units
| Micrometres | 250 |
|---|---|
| Millimetres | 0.25 |
| Centimetres | 0.025 |
| Metres | 0.00025 |
How it's measured
Adult body length. Goldstein 2018, Cold Spring Harbor Protocols (Hypsibius exemplaris); another study gives about 230 µm.
Sources
- par.nsf.gov: Cold Spring Harbor Protocols (Goldstein 2018): the animals are about 250 µm long.
Checked against the source on .
Could you have guessed it by eye?
Tardigrade is one of the objects in Tiny Worlds, a daily size comparison game: you stretch a shape to the size you think is right beside one you know.