Running Pace Calculator

Running Pace Guide

What's the difference between Pace and Speed?

Pace and speed describe the same physical reality from opposite ends of the relationship, and runners and physicists tend to use different conventions. Pace (typically minutes per kilometre or minutes per mile) is how runners think about effort — it answers 'how long does it take me to cover one km?' Lower pace numbers mean faster running. Speed (km/h or mph) is the physics-style measure — distance covered per unit time, where higher numbers mean faster. They're inversely related: 5:00/km = 12 km/h (because at 5 minutes per km you cover 12 km in an hour); 6:00/km = 10 km/h; 4:00/km = 15 km/h. The conversion: km/h = 60 ÷ (minutes per km), and min/km = 60 ÷ (km/h). For miles: 5:00/mile ≈ 12 mph; 8:00/mile = 7.5 mph; 10:00/mile = 6 mph. Why do runners use pace rather than speed? Because at the speeds humans run, pace gives clean round numbers that scale nicely (5:00/km is a benchmark; 12 km/h is an awkward speed to think about during a run). Treadmill conversions: 10 km/h on the display = 6:00/km pace; 12 km/h = 5:00/km; 14 km/h = 4:17/km; 16 km/h = 3:45/km. The general 'pace = 60 ÷ km/h' formula lets you decode any treadmill speed into running pace. This calculator handles both directions and converts between km and miles.

What do I need to know about Race Time Predictions?

Predicting your race time at a new distance from a known race time at another distance uses the Riegel formula: T2 = T1 × (D2/D1)^1.06, where T1 and T2 are the times and D1 and D2 the distances. The 1.06 exponent (rather than a simple 1) reflects the fact that longer races are proportionally slower — you simply can't sustain 5 km pace for a marathon, however well trained. The formula encapsulates this physiological reality from empirical data across many runners. A worked example: if you've run a 5 km in 25 minutes (5:00/km pace), the Riegel formula predicts your 10 km time at 25 × (10/5)^1.06 ≈ 25 × 2.085 ≈ 52 min (5:12/km — slightly slower than 5km pace). For a half marathon (21.1 km): 25 × (21.1/5)^1.06 ≈ 25 × 4.65 ≈ 116 min, about 1:56 (5:30/km). For a marathon: 25 × (42.2/5)^1.06 ≈ 25 × 9.7 ≈ 242 min, about 4:02 (5:44/km). The formula is most accurate when both your training and your race distance match — a sprinter's Riegel prediction for the marathon would be optimistic because they lack endurance training; an ultrarunner's 5 km prediction from a marathon time may be conservative. As a rule, predictions are most reliable when comparing distances within the same general range (5 km to half marathon works well; 1 km to marathon stretches the formula). This calculator applies Riegel and gives predictions for common race distances from any one input.

What's the key thing to understand about Training Paces by Zone?

Training at the right paces — not all of them being 'race pace' — is the foundation of running improvement, and most amateur runners spend too much time at moderately-hard paces that don't optimally develop fitness. The common framework distinguishes several zones: easy/recovery runs should be 60–90 seconds per km slower than 10 km race pace — easy enough to hold a conversation, designed to build aerobic base and aid recovery; this should make up the majority (often 70–80%) of weekly mileage. Long runs are typically 45–75 seconds slower than 10 km pace, building endurance over time. Tempo or threshold runs are roughly at 10 km–half marathon race pace — 'comfortably hard', sustainable for 20–40 minutes, building lactate clearance. Intervals at VO2max pace are run at slightly faster than 5 km race pace, in short reps with recovery between (e.g. 6 × 800 m), building maximum aerobic capacity. Speed/repetition work is faster still, used sparingly. The polarised training model — lots of easy running plus a small amount of hard work, very little 'moderate' — has strong evidence behind it for endurance development. The most common mistake is running easy runs too hard, which prevents both recovery and the high-quality hard sessions that drive improvement. A pace calculator helps you set targets for each zone from a single race time, ensuring easy runs really are easy and hard runs are properly hard.

What do I need to know about Converting Between Treadmill Speed and Pace?

UK treadmills show km/h; US treadmills show mph. To convert km/h to min/km: divide 60 by the speed. So 10 km/h = 6:00/km, 12 km/h = 5:00/km, 15 km/h = 4:00/km. 1 mph = 1.609 km/h. A 6 mph treadmill setting = 9.66 km/h = 6:13/km pace.

What Pace Zones Suit Different Race Distances?

Race pace isn't a single number — it shifts meaningfully depending on the distance being raced, because the balance between aerobic and anaerobic energy systems changes with race duration. A 5K is raced at close to, or just below, lactate threshold intensity for most runners, meaning it's hard but theoretically sustainable for slightly longer than the race itself if pushed. A 10K is raced at a slightly lower percentage of maximum effort than a 5K, typically a few percent slower per kilometre, because the longer duration requires a small additional margin of sustainability. A half marathon shifts further still toward aerobic-dominant pacing, commonly run at somewhere around 85-90% of 5K pace intensity for most runners, while the marathon moves further again toward a pace that's heavily dependent on fat-burning efficiency and glycogen management rather than raw aerobic power, typically landing well below half-marathon pace per kilometre for all but the most aerobically gifted or marathon-specifically-trained runners. This is part of why simple percentage-based pace predictions (assuming a fixed drop-off per doubling of distance) become less reliable the further apart the two distances being compared are — the physiological demands of a 5K and a marathon are different enough that a runner's relative strength at one doesn't automatically predict proportional performance at the other.

How Should Pace Targets Adjust for Hills and Heat?

Flat-ground pace targets need meaningful adjustment when hills or heat are part of the run, because both increase physiological cost without necessarily showing up as a pace change you'd expect from fitness alone. On hills, the general rule of thumb used by many coaches is that effort, not pace, should stay roughly constant — meaning pace should slow on the way up and is allowed to recover somewhat on the way down, rather than trying to hold a flat-ground pace target uphill, which would require a disproportionate effort increase. A commonly cited adjustment is roughly 10-20 seconds per kilometre of pace lost per percent of gradient on sustained climbs, though this varies with fitness and how experienced a runner is at pacing hills. Heat has a similar effect through a different mechanism: as core and skin temperature rise, blood flow is diverted toward the skin for cooling, leaving less available for working muscles, and heart rate climbs at a given pace well above what it would be in cool conditions — this is sometimes called cardiac drift. Experienced coaches generally recommend slowing goal pace by a few percent for every few degrees above around 15-18°C (59-64°F), with the exact adjustment depending on humidity, acclimatisation, and how direct the sun exposure is. In both cases, pacing by heart rate or perceived effort rather than rigidly chasing a flat-ground pace number produces a more appropriate and sustainable effort.

Worked Example: Converting a 5K Target Time to Required Pace

A runner aiming for a 25-minute 5K needs to average 25 ÷ 5 = 5:00 per kilometre, or roughly 8:03 per mile. Breaking that into splits for pacing purposes, a slightly conservative start might target 5:05 for the first kilometre, holding or gradually negative-splitting down to around 4:55 for the final kilometre as the finish approaches — a common pacing strategy since starting too fast relative to target pace is one of the most frequent reasons runners fail to hold target pace all the way to the finish in shorter races.

What should I know about Grade-Adjusted Pace?

Grade-adjusted pace (GAP) is a metric used by some running watches and platforms to convert an uphill or downhill effort into the 'equivalent' flat-ground pace, since running the same raw pace uphill clearly costs more effort than on flat ground. This is a separate concept from simply slowing target pace for hills, covered elsewhere on this page, because GAP works backwards from a recorded run to estimate effort, rather than forwards from a flat-ground target to a hill-adjusted target pace before a run even starts — the two are complementary tools used at different points in training and racing.