Calculating pi by throwing darts (python 2.7)

Can´t find the problem with this code, at the end its supossed to print pi but it print numbers close to 2 instead

import random
def kasta_pil():
    x = random.random()
    y = random.random()
    return (x, y)
def inne_i_cirkel(x, y):
    if x + y <= 1:
        return True
    else:
        return False
while True:
    try:
        z = int(raw_input("Hur många pilar vill du kasta: "))
    except ValueError:
        print "Invalid input"
        continue
    if z < 1:
        print "Måste vara åtminstone 1"
    else:
        break
pilar_i_cirkel = 0.0
for i in range(z):
    x, y = kasta_pil()
    if inne_i_cirkel(x, y):
        pilar_i_cirkel = pilar_i_cirkel + 1
print "Pi är ungefär: ", (pilar_i_cirkel / z) * 4