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Speed Training Pace Calculator Interval Pace, Reps, and Rest by Goal Race Time

Let's face it — most interval pace tools hand you a single number and stop there. They don't tell you how many reps to run, how long to rest, or whether that number even holds up on a treadmill. I've coached interval sessions on the track for over twenty years, and a pace figure on its own is only half a session plan.

So what pace should you run your intervals at? Interval pace isn't a fixed number — it's derived from your current fitness, best proxied by a recent race time. As a rule of thumb, interval pace for reps of 400m to 1600m sits roughly at your current 5K race pace to slightly faster, 5 to 10 seconds per kilometre quicker, depending on how short the rep is. The shorter the rep, the faster it should feel relative to 5K pace.

Enter your own time in the calculator below and I'll turn that principle into an exact number for you — plus the reps and rest to go with it. And if you're not yet sure whether you should be doing structured intervals at all, make sure you're ready for speed training first.

The Calculator: Enter Your Time, Get Your Paces

This calculator uses the same underlying pace-derivation method as the site's full training pace zones tool, so the two won't quietly disagree with each other — this one simply breaks the interval zone down into rep-specific splits for 400m, 800m, 1200m, and 1600m reps.

If your only recent result is at a different distance, use the race conversion calculator to convert it first, then come back and enter it below.

Enter your race distance and finish time, and let the calculator do the rest.

Interval Pace Calculator Enter a recent race performance below — ideally a 5K or 10K.
Race distance		KilometresMiles
Finish time		: : (hh:mm:ss)
400m rep
800m rep
1200m rep
1600m rep

Choosing Rest Intervals by Rep Distance

A pace number on its own doesn't tell you how long to rest, and that's where most calculators stop. Here's the rest-by-distance table I coach to:

Rest should be active — an easy jog, not a full stop — except for the newest interval runners, who are better off walking. One thing worth remembering: rest gets shorter, not longer, as your fitness improves. More on that in the recalculating section below.

How Many Reps Is Right for Your Fitness Level

Pace and rest still don't answer the volume question — how much of this should you actually do in one session? I tie total quality-rep volume to experience level, not just weekly mileage:

Beware of jumping volume brackets in a single session. Build reps or distance, not both, in the same week — that's exactly the mistake I see most often, a runner adding both more reps and a faster pace after one good session, which is when overuse niggles tend to show up. For how this volume progresses across a full block, see the 8-week speed training mesocycle.

Worked Examples by Goal Time (5K, 10K, Half Marathon)

Numbers make more sense with a full session attached to them. Here are three, built from the pace-derivation method above:

These three are illustrative examples built from the pace-derivation method above — they're not a substitute for entering your own time in the calculator.

Track vs. Treadmill vs. Road Pace Adjustments

None of the pace tools I've checked say anything about surface. Here's the adjustment I coach to.

Track — run reps to the exact distance at the stated pace. No adjustment needed.

Treadmill — set your pace 3 to 5 seconds per kilometre slower than the calculated outdoor pace. The belt does some of the work for you and there's no wind resistance, so a straight match runs slightly too easy. My full treadmill-specific pacing guidance covers this in more depth.

Road or trail — without track markings, target the same pace by GPS or effort, then adjust further slower for hills, turns, or uneven terrain. Effort should still feel like controlled hard, not a fixed number regardless of the surface underfoot.

No Recent Race Time? How to Estimate Instead

No result on the books? You've got two practical routes.

The first is a recent hard training effort — an all-out, timed 3K or 5K time trial on a flat, familiar route. Use it exactly as you would a race time. The second, if a time trial genuinely isn't possible, is your current easy pace and perceived effort combined with your training age, used as a rough placeholder rather than a precise input.

Beware: an estimate that's wrong in either direction undermines every number on this page. Recalculate for real within 4 to 6 weeks, once an actual time trial or race is run.

When and How Often to Recalculate Your Paces

Pace isn't a one-time number. Recalculate after any new race or genuine time trial. As a default, revisit your numbers every 6 to 8 weeks through a structured block, even without a race in that window — fitness shifts faster than most runners re-check their figures.

Here's the practical trigger for recalculating early rather than waiting for the calendar: if your reps consistently feel easier than controlled hard at the calculated pace, that's your signal. Pace changes get built into a training block, not adjusted mid-week — the mesocycle page above walks through exactly how.

Run the numbers, respect the rest, and recalculate before your paces go stale — that's a sensible way to train, not an over-engineered one. Head back to the full speed training guide for how this pace work fits into the bigger picture.

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