"I need to use the correct scale."
Translation:Saya harus menggunakan skala yang benar.
I agree with Femmy. Butuh is also kind of similar, means "need" but seems to be more used to describe things you need/require in life, where perlu seems to me to be closer to Harus to describe what you need or have to do. Also sometimes see "usah" used for need, for example "Tidak usah khawatir" "No need to worry"