from tkinter import *

window=Tk()

def km_to_miles():
    #print(e1_value.get())
    miles=float(e1_value.get())*1.6
    t1.insert(END,miles)


bi=Button(window, text="Execute", command=km_to_miles)
#bi.pack()
bi.grid(row=1,column=2)

e1_value=StringVar()
e1=Entry(window,textvariable=e1_value)
e1.grid(row=0,column=1)

t1=Text(window,height=1,width=20)
t1.grid(row=0,column=2)

window.mainloop()