if else combined with calculations

I'm writing a BMI calculator program, with options for both metric and imperial. My problem is when I try it for metric, the program must be running the numbers through the imperial equation, because I am getting a crazy answer. Here is my code:

var1 = "imperial"

print "Do you use imperial or metric?"
ans = raw_input()
var1 = ans
if var1:
    print "What is your weight?"
    weighti = float(raw_input()) 
    print "What is your height?"
    heighti = float(raw_input())
    print "Your body mass index, BMI, is", weighti * 703 / heighti**2
else:
    print "What is your weight?"
    weightm = float(raw_input())
    print "What is your height?"
    heightm = float(raw_input())
    print "your body mass index, BMI, is", weightm / heightm**2