There's no hard and fast rule for the minimum number of songs for an effective Spotify playlist. However, it's generally suggested to have at least 20-25 songs. This ensures variety and a listening experience of about 1 to 1.5 hours, depending on the length of the songs. Of course, the number can vary based on the purpose of the playlist. For instance, a workout playlist might be shorter, while a playlist for a road trip might be much longer.