If you're Googling "how long is a marathon?" chances are you're inspired by marathon season.

First up is the London Marathon, which takes place on Sunday, October 3. For those of you who have been buoyed by marathon fever, here's everything you need to know about this distance.

The marathon is 26.2 miles (about 42.19 km).

There is a reason for the very specific distance; it was not set until the 20th century. The modern marathon was inspired by a legend that in 490 B.C. an ancient Greek messenger ran from Marathon to Athens (a distance of about 25 miles) carrying news of a Greek victory over the Persian army. After completing his run, he collapsed and died. To commemorate this achievement, the marathon distance for the 1896 Olympics was set at 40 kilometers.

However, at the 1908 Olympics in London, the course was extended. This was reportedly because Queen Alexandra wanted the race to start on the lawn of Windsor Castle so that younger members of the British royal family could watch the runners.

The race finished in front of the Royal Box at the Olympic Stadium, which was 26.2 miles away.

According to data from a study of race results from over 70,000 events from 1986 to 2018, the average marathon finish time for U.S. runners was 4 hours and 42 minutes. The average marathon finish time for men in the U.S. is 4 hours 31 minutes, while the average marathon finish time for women is 4 hours 57 minutes.

The men's world record for the marathon distance is 2 hours 1 minute 39 seconds, set by Eliud Kipchoge at the 2018 Berlin Marathon. The women's marathon world record is 2 hours 14 minutes 04 seconds, set by Brigitte Kosgei at the 2019 Chicago Marathon.

If you were to walk 26.2 miles, it would take 6 to 9 hours. If he walked faster, he would probably finish in 6-7 hours, but at his natural walking pace, it would take longer.

The half marathon is 13.1 miles (about 21.09 km).

According to the same data collected by RunRepeat, for U.S. runners, the average finish time for a half marathon is 2 hours and 10 minutes. Digging deeper, the average male runner in the U.S. runs a half marathon in 2 hours and 2 minutes, while the average female runner finishes in 2 hours and 16 minutes.

The male world record for the half marathon distance is 57:32 set by Kibiwot Kandi in the half marathon held as part of the Valencia Marathon in 2020. The women's world record for the half marathon distance is 1 hour, 4 minutes, and 31 seconds, set by Ababel Ishane at the 2020 Las Alhaimas Half Marathon.

The 10 km is 10 kilometers, or 6.21 miles.

The average finish time for 10 km in the U.S. is 1 hour and 1 minute. The men's average time is slightly faster at 58 minutes and the women's slightly slower at 1 hour 6 minutes; the world records for the 10 km are Joshua Cheptegei's 26:11 for the men and Almaz Ayana's 29:17 for the women.

The 5k is 5 km, 3.1 miles.

The average 5k time for American runners is 39 minutes. The men's average is a faster 35 minutes and the women's average is slower at 41 minutes; the world records for the 5k are Joshua Cheptegei's 12:35:36 for the men and Lotesenbet Gidey's 14:06:62 for the women.