Last updated: 2026-05-22

Reading Your Splits Off the Lap Clock

Interval training only works if you hit the right pace — too slow and the session loses its purpose, too fast and you fade before the last rep. On a 400 m track the simplest way to stay honest is to know your split time for each repeat distance in advance. This calculator turns a target pace into those splits: enter the pace you want to train at, and read the target time for 200 m, 400 m, 800 m, 1000 m, 1600 m and the other standard repeats straight off the table.

How It Works

A repeat of distance $d$ run at pace $p$ (time per unit distance) takes:

$t = d \cdot p$

That is the whole calculation. The value of the tool is doing it for every standard track distance at once, in whatever pace unit you think in, so you never have to convert "4:00 per kilometre""6:26 per mile" into "what should the clock say at 600 m" mid-workout.

The speed output is the same target expressed as km/hmph — handy when the workout moves to a treadmill, which is calibrated in speed rather than pace.

Choosing Your Interval Pace

The calculator does not invent your pace for you — that is a coaching decision. The widely used framework (popularised by Jack Daniels) distinguishes two efforts:

• Interval (I) pace — run for aerobic power, in efforts of about 3–5 minutes. It is close to your current 3 km–5 km race pace: the pace you could just about hold for a hard 5 km today. Typical reps: 400 m, 800 m, 1000 m, 1200 m.
• Repetition (R) pace — faster and sharper, used to build speed and running economy in shorter reps. It is close to your mile / 1500 m race pace. Typical reps: 200 m, 300 m, 400 m.

A practical starting point: take a recent race result, find the pace, and enter it here. If your most honest recent effort is a 5 km, that pace is a sound interval-pace target; for repetition work, enter a pace roughly 10–15 seconds per kilometre faster.

Why These Distances

A standard outdoor track is 400 m per lap, so workouts are built from lap fractions and multiples:

Because the table is keyed to these distances, the split it gives you is exactly what the lap clock should read as you come through — no mental arithmetic while your heart rate is at the ceiling.

Practical Scenarios

1. A Classic VO2-max Session

Planning 5 × 1000 m at 5 km race pace5 × 1000 m at 5 km race pace: enter your 5 km pace, read the 1000 m split, and that is the time to hit on each of the five reps. If the splits start drifting slow, the session is telling you the pace was too ambitious.

2. Sharpening Speed

For a 200 m–400 m repetition workout, enter your mile / 1500 m race pace. The 200 m and 400 m splits become your targets for short, fast, full-recovery reps.

3. Pacing a 1500 m / Mile Time Trial

Enter your goal mile / 1500 m pace and the 400 m split shows the even-pace lap time for a 1600 m time trial — a simple way to rehearse the pacing before race day.

Caveats

• The split is for the fast repeat only. Recovery jogs and standing rests are separate; add them yourself when planning total session time.
• Even pace is assumed. Real reps usually start a touch fast and drift; treat the split as the average to aim for.
• Pace targets should come from real data. Base your interval pace on a recent race or a coach’s guidance, not a hopeful guess — the calculator is only as good as the pace you put in.