What this result means
Repeats are an interval session with a locked work distance. This page locks 400 m. You set pace, how many, and rest between. The interval workout calculator lets the work distance float.
The 400m split calculator is a single time trial. This page is the set.
10 × 400 at 5:00/km with 90 s rest: each rep 2:00, work 20:00, rest 13:30 (nine intervals), session 33:30, work 4.0 km.
6 × 400 at 3:20/km with 2:00 rest is a harder aerobic session than 8 × 400 at 5:00 with 1:00 rest. The clock will tell you; coaching still picks the one you meant.
Calculation method
Work time = 0.4 × seconds per km. Total work = work × reps. Total rest = rest × (reps − 1). Session = work + rest.
Exact arithmetic. Last rep has no rest after it.
No warmup, no cooldown, no jog rest vs stand rest. Rest seconds are whatever you type.
Frequently asked questions
How long is 8 × 400 at 4:00/km with 60s rest?
1:36 each, 12:48 running, 7:00 rest, about 19:48 session, 3.2 km work.
Does rest include jogging?
The rest field is seconds on the clock. Jog or stand; the math does not care.
Can I change the work distance?
Use the interval workout calculator. This page is 400 m only.