Average ACT: 29. The average ACT score composite at UCSD is a 29. The 25th percentile ACT score is 26, and the 75th percentile ACT score is 31. In other words, a 26 places you below average, while a 31 will move you up to above average. There's no absolute ACT requirement at UCSD, but they really want to see at least a 26 to have a chance at being considered.