S c t. By using the formula from this video you can even calculate light year. In 1983 an international commission on weights and measures set the speed of light in a vacuum at the calculation we use today.
Light Years Lets work out how far a light year is.
Simply input two of three variables speed distance and time and the form will calculate the third for you. Write the formula for distance. Light Years Lets work out how far a light year is. Therefore a light year is exactly 94607304725808 kilometers.