Both the classical and acoustic guitar are of acoustic nature. However, the difference between the classical and acoustic guitar is their different shapes, sizes, and materials used to make them. Classical guitar is made of nylon strings, while acoustic guitar is made of steel strings. The shape of the classical guitar is a bit smaller and more in width than that of the acoustic guitar. Classical guitars rarely change their size, while the acoustic steel guitar comes in numerous sizes.
The classical guitar can never be transformed into a steel guitar. The classical guitars are made up of light wood and cannot bear the pressure produced from the steel strings located on the neck or nut of the guitar. Acoustic guitars can be a nylon type of classical guitar. Also, classical guitars are used mostly for playing classical music, while the acoustic guitar is used for pop, jazz, rock, or blues.