How long is a light year in terms of miles?

A light-year is a unit of distance. It is the distance that light can travel in one year. Light moves at a velocity of about 300,000 kilometers (km) each second. So in one year, it can travel about 10 trillion km.

More precisely, one light-year is equal to approx 9.50 billion kilometers or 5.88 billion miles.

At ephemera time midnight january 1st 1900 - it was 365.24219878 days and 5,878,500,600,00 miles (very old Guiness Book of Records (when it was a reference book))

Light travels at 186,000 miles per second. Therefore 60x60x24x365=seconds in a year 31,536,000 x 186,000 =miles in a lightyear. My calculator doesn't have enough digits.

Silly me. 5,865,696,000,000

To be extremely precise, a year has 365.25 days, making a light year approximately 5,869,713,600,000 miles in length.

To be even more precise !
One light year (1 ly) is the distance that light travels in one year. In one second light travels 186,282 miles or 299,793 km. Since there are in a tropical year about 31,569,260 seconds, we can find the length of a light year by multiplying velocity by time to give 5.88 trillion miles (9.46 trillion km).
Of course this is an American trillion (9 zeros) not an English trillion. (18 zeros)

In England a lightyear has a value of 5.88 BILLION miles (9 zeros)

Note that the quoted figure for the speed of light is ONLY in a TOTAL VACUUM !