Running Pace Calculator — Finish Time, Distance & Pace Converter

They measure the same thing upside down, and mixing them up is the most common source of confusion in running.

Pace is time per unit of distance — minutes and seconds per kilometre or mile. Speed is distance per unit of time — kilometres or miles per hour. Lower pace means faster; higher speed means faster, which is exactly why they get tangled.

Converting between them is a single division in either direction:

Pace (min/km) = 60 ÷ Speed (km/h) and Speed (km/h) = 60 ÷ Pace (min/km)

A 5 min/km pace is 60 ÷ 5 = 12 km/h. A 10 km/h runner is at 60 ÷ 10 = 6 min/km. The same relationship holds for miles and mph.

Use pace for running. Training plans, race targets, and split times are all expressed in pace, because runners think in terms of "how long will this kilometre take." Every race strategy you will read is written in pace.

Use speed for machines and crossover sports. Treadmills are calibrated in mph or km/h, not pace, so converting is unavoidable if you train indoors. Cycling, rowing, and swimming all use speed conventions too, which matters if you are a triathlete reading across disciplines.

Hold a given pace and your finish time is fixed arithmetic. The table below uses the official distances — 5 km, 10 km, 21.0975 km for the half marathon, and 42.195 km for the marathon — which matters more than people expect: rounding the marathon to 42 km makes a 4-hour prediction 67 seconds optimistic, and that is the kind of error that costs someone a goal at the finish line.

One caution before reading across the rows. These are the times you get if you hold that pace the whole way, which is a large if over a marathon. Holding 5:00/km for a 5K and holding it for 42 km are entirely different athletic problems, and the longer the race, the more your realistic pace drifts from your short-distance pace.

Look at the two middle rows of that goal table. A sub-2-hour half marathon and a sub-4-hour marathon require the same pace — 5:41/km, or 9:09/mile. This is not quite a coincidence: the marathon is exactly twice the half, so doubling the distance and doubling the target time lands on an identical pace requirement.

It is genuinely useful as a mental benchmark. If you can hold 5:41/km for 21 km, you have proven you can run the pace; the marathon then asks whether you can hold it for twice as long, which is a question about endurance rather than speed. Most runners who miss a sub-4 marathon do not miss it because the pace was too fast — they miss it because they could not sustain a pace they were fully capable of running.

The Boston Qualifier row deserves a note too, because the standard moved. The BAA tightened its qualifying times by five minutes for the 2026 race, so the men's 18–34 standard is now 2:55:00 rather than the 3:00:00 many runners still train toward. And meeting the standard is not the same as getting in: the field is capped, so entries are accepted fastest-first, and the 2026 race only admitted runners who beat their standard by more than four and a half minutes. If Boston is the goal, treat the published time as a floor and build a five-minute cushion on top of it.

Most amateur runners run nearly every session at the same moderate intensity — hard enough to be tiring, easy enough to complete — and then wonder why they stop improving. Training zones exist to break that pattern.

Zone 1 — Recovery (roughly 60–65% of max heart rate). Very easy, fully conversational, typically 2–3 min/km slower than race pace. Its job is circulation and recovery between hard sessions, not fitness. It should feel almost pointlessly slow.

Zone 2 — Aerobic base (roughly 65–75%). Comfortable, able to hold a conversation in full sentences, around 1–2 min/km slower than 10K pace. This is the most important and most neglected zone for amateur runners. It builds capillary density, mitochondrial function, and fat metabolism — the aerobic engine everything else is built on. It is also boring and feels too easy, which is precisely why people skip it.

Zone 3 — Tempo (roughly 75–85%). Comfortably hard, short sentences only, approximately 10K race pace. This is lactate threshold work, and it is the zone amateurs overuse — hard enough to accumulate real fatigue, not hard enough to drive the adaptations that intervals produce.

Zone 4 — Threshold (roughly 85–90%). Hard, barely able to speak, around 5K race pace. Used in sustained intervals to raise the intensity you can hold before lactate accumulates faster than you clear it.

Zone 5 — VO2max (roughly 90–95%). Very hard, speech impossible, faster than 5K pace. Short intervals only, used to develop maximum oxygen uptake.

The 80/20 rule is the single most transferable finding in endurance training. Elite runners spend roughly 80% of their training time in Zones 1–2 and only 20% in Zones 3–5. The typical recreational runner inverts this, spending most of their week in Zone 3 — the "comfortably hard" middle ground that feels productive and delivers the least adaptation per unit of fatigue. Going genuinely easy on easy days is what makes it possible to go genuinely hard on hard days. To anchor these zones to your own heart rate rather than guessing, the target heart rate calculator works out the beats-per-minute range for each.

A negative split means running the second half of a race faster than the first. It is how nearly every distance world record has been set, and it is how a small minority of recreational runners race.

The data from major marathons is consistent and unflattering: roughly 80% of recreational runners positive split — going out too fast and slowing in the second half — while only around 15% achieve a negative split. Almost everyone knows the theory. Almost nobody executes it, because the first few kilometres of a race feel easy enough that holding back seems absurd.

Why going out fast costs more than it gains. Running 10 seconds per kilometre faster than goal pace early in a marathon does not bank 10 seconds per kilometre — it typically costs more than two minutes over the second half, because burning through glycogen faster than you can replace it accelerates the point where you slow dramatically. You are not saving time; you are borrowing it at a punitive rate. Your aerobic system also needs 10 to 15 minutes to fully engage, so the effort in the first mile is genuinely misleading — perceived effort at kilometre 1 and kilometre 35 are not remotely comparable measurements.

How to actually do it. The first mile should feel embarrassingly easy — if it feels like goal pace, you are going too fast. Target the first half around 30 to 60 seconds per mile slower than goal pace. Use the crowd as a diagnostic: if you are passing people in the first 10K, you went out too fast, because the people around you at that point are making the same mistake. The aim is to be the person doing the passing between miles 20 and 26, which is the part of the race that actually determines your finish time.

A worked plan for a sub-4:00 marathon. An even split needs 5:41/km throughout. A negative split targets the same finish differently: run the first half at 5:47/km for a 2:02:01 halfway split, then lift to 5:35/km for a 1:57:48 second half. Total: 3:59:48. Those six seconds per kilometre in the opening half feel like nothing on the day — and they are what leaves you with something in reserve when the second half starts asking real questions.

Treadmills are calibrated in miles or kilometres per hour, so every indoor session requires a conversion before it means anything in pace terms. The table below does it both ways, and adds the finish times each speed actually produces — which is the column worth reading carefully, because treadmill speeds are routinely mislabelled with race goals they do not deliver.

Two of those mislabels are worth calling out specifically. 6.5 mph is frequently described as sub-2-hour half marathon pace, and it is not — it produces a 2:01:01 half. You need 6.55 mph to break two hours, and since most treadmills adjust in 0.1 increments, that means 6.6 mph. Similarly, 8.0 mph is not sub-3-hour marathon pace; it produces a 3:16:38. Breaking three hours takes 8.74 mph, closer to 8.8 on the console. Setting a treadmill to a speed that feels like your goal and assuming it matches is how people arrive at race day having trained 16 minutes slow.

Even with the conversion correct, the same number means something different indoors. A treadmill removes air resistance, which at recreational speeds accounts for a meaningful share of the effort, and the belt provides a small amount of assistance as it pulls your foot backward through the stride. The result is that treadmill running is typically 5 to 10 seconds per mile easier than the equivalent road pace.

The standard correction is to set a 1% incline, which approximately equalises the energy cost to running the same speed outdoors. It is not a precise adjustment at every speed — the effect of air resistance grows with pace, so 1% slightly over-corrects for slow running and under-corrects for fast running — but it is close enough for training purposes and far better than no correction at all.

Cutting the other way, indoor conditions are often harder than the numbers suggest. Gyms are usually warmer and less ventilated than outdoor air, and heat raises heart rate independently of pace, so the same effort can feel considerably worse on a treadmill in a crowded gym than on a cool road. If your heart rate on the treadmill sits well above what that pace normally produces outdoors, the room is a more likely explanation than lost fitness.