What are the chances of getting pregnant while taking the birth control pill responsibly?

1/333 women annually. For women taking birth control pills (ocp's) properly and consistently, the chance of pregnancy is reported to be 0.3% per year, or 1 pregnancy in 333 women each year. The actual pregnancy rate in the "real world" is reported to be at least 3% on ocp's, or 1 pregnancy in 33 women each year.
Pregnancy on pill. The birth control pills are about 99% effective when taken properly and not interfered with by certain conditions e.g. Taking certain antibiotics, or anti-fungal agents or if the pill is missed or vomited up within an hour of taking it etc. About 8 out of 100 couples per year will have a pregnancy while taking birth control pills as directed.

Related Questions

What are the chances of getting pregnant if I had sex without a condom but I'm on birth control pill?

Conception rates. Even with perfect use of the pill most contraceptive makers state the pills is 95%-97% effective. So, that would give you a 3%-5% rate of pregnancy with the pill.

Chances of getting pregnant when taking birth control pill at same time daily and using pull out method every time?

Very, very little. Wouldn't worry. In real life, a woman properly taking birth control pills has a very low chance of pregnancy. Combine that with the "pull-out" method, and she will have very, very little chance of pregnancy. Life can be surprising sometimes, so in the rarest of occasions a woman in such a situation might become pregnant... but that's life.

If I take the birth control pill 12 hours later the usual, does that give me a whole new chance of getting pregnant?

Shouldn't, but. Missing pills does increase the chance of ovulation occurring, but if you remembered it 12 hours later, then took the next pill on time (in another 12 hours) - the chance of getting pregnant due to that - is low.