UK Running Pace Calculator

Whether you are checking your pace from a recent run or setting a goal for an upcoming race, this calculator works out your running pace per kilometre and per mile, your speed, and predicts your likely finish time at common race distances based on your current form, using the same formula many online race calculators rely on.

How to use the running pace calculator

Enter the distance you ran, in kilometres or miles, and your finish time in hours, minutes and seconds. The calculator instantly shows your pace per kilometre and per mile, your average speed, and predicted finish times for 5K, 10K, half marathon and marathon distances based on that same effort level.

How the calculation works

Pace per kilometre is simply your total time divided by your total distance in kilometres, and pace per mile converts this using the standard 1.60934 kilometres to a mile conversion. Speed is the reverse calculation, distance divided by time, expressed in kilometres per hour and miles per hour.

Race predictions use Riegel's formula, T2 = T1 × (D2/D1)^1.06, a widely used method for estimating a finish time at a different distance from a known time and distance. The formula assumes a small, realistic slowdown in pace as distance increases, rather than assuming you could hold exactly the same pace for a much longer distance.

Worked example

A runner completing 10km in 50:00 is running at a pace of exactly 5:00 per km, or around 8:03 per mile, at a speed of 12 km/h (about 7.5 mph). Using Riegel's formula, that same runner's predicted times are roughly 23:59 for a 5K, 1:50:19 for a half marathon, and 3:50:01 for a full marathon, assuming similar training and conditions across all distances.

For a longer example, a runner completing a half marathon in 1:45:00 is running at almost exactly 4:59 per km. Using the same formula, that performance predicts a 10K time of around 47:35, and a marathon time of around 3:38:55, a prediction that tends to be more reliable than one based on a much shorter race, since half marathon and marathon distances share more in common in terms of pacing and endurance demands.

Common training paces explained

Most structured running plans work with several different training paces, not just race pace. Easy or recovery pace is noticeably slower than race pace and makes up the bulk of weekly mileage for most runners, building endurance with lower injury risk. Tempo pace sits comfortably faster than easy pace but a little slower than race pace, used for sustained efforts that build the ability to hold a strong pace for longer. Interval pace is faster than race pace, run for shorter bursts with recovery in between, aimed at improving speed and running economy. Your predicted race pace from this calculator is a useful reference point for working out roughly where each of these training paces should sit relative to your current fitness.

Pacing strategy: even splits versus negative splits

How you distribute your pace across a race matters almost as much as your overall time. Starting too fast is one of the most common mistakes in distance running, since the extra effort required to hold an unsustainable early pace often causes a much larger slowdown later in the race than the time gained at the start. Many experienced runners and coaches favour even splits, running at a consistent pace throughout, or negative splits, running the second half slightly faster than the first, both of which tend to produce a more comfortable and often faster overall race than starting too aggressively and fading.

Improving your pace over time

Pace generally improves gradually, through a mix of consistent training, an appropriate balance of easy and harder sessions, and allowing enough recovery between efforts for the body to adapt. Increasing weekly mileage too quickly is a common cause of injury, which then interrupts training far more than a slightly slower, steadier build-up would have. Many runners also find that some general strength training, particularly for the legs and core, alongside running-specific sessions, helps improve running economy and resilience over time, on top of running itself.

Common mistakes to avoid

A common mistake is treating a predicted marathon time from a short, fast 5km effort as reliable, when in reality, endurance, fuelling and pacing become much bigger factors over a marathon distance than they are over 5km. Predictions from a longer recent race, such as a 10K or half marathon, tend to be noticeably more reliable for estimating a marathon time.

Another mistake is ignoring the conditions a time was set in. A pace run on a hilly, hot or windy course will not directly translate to the same pace on a flat course in ideal conditions, so use route and weather context alongside the raw numbers when setting a race goal.

Related calculators

If strength training is also part of your routine, our one rep max calculator estimates your 1RM from a recent lift. To plan your nutrition around your training, our TDEE calculator estimates your daily calorie needs, and our ideal weight calculator gives a general healthy weight range to consider alongside training goals, not as a target to chase aggressively. None of these figures should be treated as a strict target, since fitness and healthy weight both depend on far more than any single number. To train at the right intensity, our heart rate zone calculator works out your estimated training zones from your age.