The speed of light in vacuum is 3 x 10^8 m/s. That means in one second it travels 300000000 metres.
As we know, in one year, there are 365 days; in each day there are 4 hours; in each hour there are 60 minutes and in each minute there are 60 seconds.
Therefore, the distance traveled by light in one year = 3 x 10^8 x 365 x 24 x 60 x 60 = 1 light year = 9.4605284 × 10^{15} meters