Step-up transformer :
• Primary winding (Np) is smaller than secondary winding (Ns)
• Primary voltage (Vp) is smaller than secondary voltage (Vs).
• Primary current (Ip) is greater than secondary current (Is).
Step-down Transformer :
• Primary winding (Np) is greater than secondary winding (Ns)
• Primary voltage (Vp) is greater than secondary voltage (Vs).
• Primary current (Ip) is smaller than secondary current (Is).
So, the equation is :

Note :
Np = Primary winding
Ns = Secondary winding
Vp = Primary voltage
Vs = Secondary voltage
Ip = Primary current
Is = Primary current
Hope it helpful and useful :)