How effective is the natural family planning method for contraception?

Depends: It really depends on how regular your cycles are and how good you are at cycle counting. This method can work, but unfortunately often times does not because women sorta expect that their bodies/ovaries work like clockwork and in all honesty they don't typically do that year after year. This method really doesn't work well in teens and women closer to the age of perimenopause. Best rate 80%.

NFP methods by definition are not contraceptive, because they do not interfere with the process of conception.The woman learns to detect her fertile time and avoids genital contact during that time in order to prevent conception.Contraceptives interfere w conception. One method is Creighton Model. It has a 98.6% effectiveness rate in the prevention of pregnancy when used according to instructions