It has been estimated through the use of telescopes and gravitational methods that there are 200-300 billion stars in our galaxy. It has also been estimated through the use of deep space telescopes that there are 100s of billions of galaxies.
Given that there 200 billion stars in our galaxy and 100 billion galaxies in the universe and assuming that we are the only life in our galaxy, this would give the odds of life forming 1star/200billion stars. Using this model and assuming that all galaxies are roughly the same size in terms of stars would give at least 100 billion other stars capable producing of life.
Using these conservative estimates and given that the laws of physics and chemistry produced life on earth, it is almost a certainty that life exists elsewhere in the universe. We may never be able to prove that other forms of life exist due to the size of the universe and the fact that it is impossible to travel at or faster than the speed of light (as given by Einstein). The closest star in our galaxy is 4.2 light years away, but our model of life assumes we are the only life in our galaxy. The closest galaxy is 80000 light years away. This means that to discover life we would need to travel 80000 years at the speed of life towards the closest galaxy. We do not have the technology to travel anywhere close to these speeds.
Life does exist on distant planets you can be sure given the numbers. This estimate does not take into account the theory of religion and only accounts for facts provable in this physical world.