Imperial and Metric Spanner/Socket Converter

from fractions import Fraction

while True:
    select = str(raw_input("To convert to metirc type 'm', or imperial type 'i':  "))

    if select == str("m"):
        mm = float(25.4)
        numer = int(raw_input("Top number(numerator)? "))
        denom = int(raw_input("Bottom number(denominator)? "))
        answer = float(mm/denom*numer)
        print str(answer)+"mm"
        numer = int(0)
        denom = int(0)
        answer = int(0)

    if select == str("i"):
        sixteenth = float(1.587)
        mm = float(raw_input("Millimeters(mm)? "))
        answer = float(mm/sixteenth)
        decimal = float(round(answer))/16
        print str(Fraction(decimal))
        decimal = int(0)
        mm = int(0)
        answer = float(0)