Float - 7 digits (32 bit)
Double-15-16 digits (64 bit)
A variable of type float only has 7 digits of precision where as a variable of type double has 15 digits of precision.
An Example :
If you need better accuracy, use double instead of float.
In general a double has 15 to 16 decimal digits of precision, while float only has 7.
This precision loss could lead to truncation errors in float than double.
If you have further doubts you could write a program in java and check the precisions :