How long should tempo runs be if I’m trying to improve mile time?

Tempo is a very broad term. Sometimes my team (including milers) does shorter tempos (20-30 minutes) at a faster pace, sometimes we do 40 minute ones a little slower depending on what point in the season it is.

It really depends on where you’re at in your training cycle. Building up to ~30 minutes of volume should be good enough for most runners during the base period when aerobic development is your priority, then as you get closer to your goal races ~20 minutes of volume should be sufficient when your race pace work should take priority.

I like the standard 20 minutes. For a miler in season, I like 2 miles to keep the pace fast and legs fresh. A 4:10 miler might be able to hit 5:15 pace and not go above threshold.

Short quick answer: 4 miles

The standard tempo run at threshold is about 20 min or 3 miles for beginners, 4 miles for elites.

6-8 mile tempo runs (definitely slower than threshold pace, more likely to be hm to marathon pace) should be used for the long distance runners (10 k up to marathon).

The miler should do no longer than the standard 3-4 mile 20 min tempo, definitely, and occasionally a shorter 1.5 - 2 mile 90-95% effort time trial.

In off-season he might run his daily 6-8 mile runs at a solid pace occasionally (once or twice per week) but that is not a real tempo run, people call it an 'up-tempo' or 'steady state' run then.

I’m usually running about 50 miles a week. Easy runs are about 7 miles. Current 5k pace is 6:30 per mile. For a couple months I’ve been doing weekly 5 mile tempos. Do you think that’s too far?

There is value in tempo runs for milers (and *all events 1500 and up) of distances from 3-8 miles. Even up to 10 miles occasionally is beneficial. It depends on the athlete and their history.

*I'm purposely leaving out the 800m here. While I do think tempo runs are valuable for 800m runners, training for the 800m is a different animal and a discussion for another time.

runningislife3 wrote:

I’m usually running about 50 miles a week. Easy runs are about 7 miles. Current 5k pace is 6:30 per mile. For a couple months I’ve been doing weekly 5 mile tempos. Do you think that’s too far?

Using the first edition Daniels system, a "tempo run" is nominally 20 minutes at the pace you could race for an hour. From your 5k pace that would be 6:56 pace, so about 3 miles.

In later editions he added an extended pace/time chart that allowed for longer duration efforts at proportionally slower paces.

Other systems have their own definitions of "tempo run" ranging from about 10k pace to marathon pace. The takeaway is that distance is a function of pace and effort and "tempo run" doesn't have a universally accepted definition. If you're self-coaching then the Daniels system might be one way to go. There's a handy spreadsheet for working out paces linked below, but one still needs to read the book to set up a training plan.