A "decimal" is a type of numbers. For example : 2.5 is a number in decimal format. 2 is an integer and, in this form, it is not a decimal number but writting it 2.0 (which is equal to 2) it becomes a decimal number. So a decimal number is a number that contains digits separated with a point.

"Degree" refers to a unit of measuring the angles (as if you say "I walk 2". This sentence is not complete because we need a unit. So we say for example : "I walk 2 meters" : meter is a unit for length and degree is a unit for angles). So a right angle is 90 degrees and angles can be represented by decimal numbers like 40.5 degrees. So decimal and degrees are independant things.

Now if your question was to convert from degrees to radians that's another thing since both are units for measuring angles.

If that is the case then :

pi radians = 180 degrees where pi is a number = 3.14159... so each 1 radian = 180/pi degrees (approximately 57.3 degrees).