Instructions
Examine the turtle's shell. If it is a young turtle that does not lose its scutes, each scute will be ridged with defined rings. Usually, each ring counts as one year in the turtle's life. Therefore, a turtle with four rings is approximately 4 years old, although the number of rings will vary slightly based on whether the turtle has had enough to eat or not.
Look at the size of the turtle's scutes. Older turtles will always have larger scutes. Turtles that lose their scutes continually grow larger scutes that push off the smaller ones on top. The scutes of turtles that do not lose their scutes increase in size as the turtles age and grow.
Look at the color of the scutes. Young turtles usually have brightly colored scutes, but older turtles usually have scutes that are darker and blend in more with their surroundings.
Study the individual size of each scute to estimate how long the turtle is. The scutes of tortoises that do not shed their scutes increase in size as the tortoise's body grows. A turtle with very large scutes will be very large for its species, although its exact dimensions depend on what species it is. If the turtle is a type that does not lose its scutes, then count the number of rings on its shell to determine its age. If it is an adult, then estimate its length by determining the average length of an adult turtle of that species.
How to Measure Turtle Length & Age Using Scutes
As turtles age and grow, their scutes -- the individual plates that their shells are made of -- change as well. Some turtles, such as painted turtles, grow new scutes and shed the old ones every year. Other turtles, such as box turtles and wood turtles, have scutes that gradually increase in size. There are several ways to determine the age and length of a turtle based on what its scutes look like.