Running Pace Calculator

A running pace calculator is the most useful tool a runner can have. Whether you are chasing a sub-20 5K, a sub-50 10K, a sub-1:30 half marathon, or a Boston-qualifying marathon, knowing your pace and predicting your finish time from training data is how you race smart instead of guessing.

Common race distances and benchmark times

5K: the entry point to racing. Competitive age-group times sit between 18 and 25 minutes, which is 3:36 to 5:00 per km. 10K: a classic distance that rewards both speed and endurance. Sub-50 is a common milestone, requiring 5:00 per km. Half marathon (21.1 km): sub-1:30 demands 4:15 per km, and sub-1:45 is a popular goal at 4:59 per km. Marathon (42.2 km): sub-3:00 is 4:15 per km, sub-3:30 is 4:58 per km, and sub-4:00 is 5:41 per km. The calculator handles all of these distances and any custom distance you enter.

How to predict your race time

The most reliable predictor of race time is your current pace at the target distance. If you can hold 4:30 per km in training for a 10K, the calculator predicts a 45-minute finish. But race day is different from training: adrenaline, taper, and competition typically improve performance by 2 to 5%. Enter your training pace, not your dream pace, and let the math tell you what is realistic.

For longer races, use the "Required pace for target" mode. Enter your goal marathon time (say, 3 hours 30 minutes) and the calculator tells you the pace you need to hold: 4:58 per km. This is the single most useful number in marathon training because it tells you whether your goal is achievable from your current fitness or whether you need to adjust.

Pace zones for training

Pace is not one number. It is a spectrum. Easy runs should be 60 to 90 seconds per km slower than your marathon pace. Threshold runs sit around your 10K to half marathon pace. Intervals and VO2 max work push faster than 5K pace. The calculator helps you identify your race pace so you can anchor your training zones around it.

Pace charts: what each goal time requires

5K in 20:00 needs 4:00 per km (6:26 per mile). 5K in 25:00 needs 5:00 per km. 10K in 45:00 needs 4:30 per km (7:14 per mile), and 10K in 60:00 needs 6:00 per km. Half marathon in 1:45 needs 4:59 per km (8:01 per mile), 1:59 needs 5:38 per km. Marathon in 3:00 needs 4:15 per km (6:52 per mile), 3:45 needs 5:20 per km, 4:30 needs 6:24 per km, and 5:00 needs 7:06 per km. Enter any of those targets in the calculator and it returns the exact pace, including seconds, in both min/km and min/mile.

Converting min/km to min/mile

One mile is 1.609 km, so pace per mile is pace per km multiplied by 1.609. A 5:00 per km pace is 8:03 per mile. A 4:00 per km pace is 6:26 per mile. A 6:00 per km pace is 9:39 per mile. The calculator switches between metric and imperial so you do not have to do the arithmetic mid-training block.

Predicting a longer race from a shorter one

Riegel's formula estimates a longer-distance time as T2 = T1 x (D2 / D1)^1.06. A 20:00 5K predicts roughly a 41:30 10K, a 1:32 half marathon, and a 3:12 marathon. That prediction assumes distance-specific endurance training, so a runner with limited long-run volume will typically run slower than the model suggests over the marathon. Use it as a ceiling, not a promise.

Negative splits and even pacing

The fastest marathons are run close to even, or very slightly negative, with the second half matched or a touch quicker than the first. A common failure is banking time early: running 10 seconds per km faster than goal pace for the first 15 km typically costs more than a minute per km over the final 10 km. Set your goal pace with the calculator, then hold it.

Adjusting pace for heat, hills and wind

Expect to lose roughly 2 to 4% of pace once temperatures exceed 20C, and more again in high humidity where evaporative cooling is impaired. Each 1% of gradient costs around 12 to 20 seconds per km on the climb and returns only part of it on the descent. Headwind is the least forgiving of the three. Recalculate your target pace against realistic conditions rather than the perfect day you trained for.

Fueling for long runs and marathons

For efforts over 60 to 90 minutes, carbohydrate fueling is non-negotiable. A high-carbohydrate fueling strategy lets you absorb more energy per hour without GI distress. Most runners need 30 to 90 g of carbs per hour for marathons and ultras, and the how much sodium you actually need depends heavily on your sweat composition. One serving of Hydrax Core per hour delivers 980 mg of sodium and a 2:1 dual-carb system. Take Hydrax Primer before long sessions to pre-load electrolytes. For events over 2 hours, read A practical approach to gut training to prepare your digestive system for higher fuel intake. And understand why osmolality matters for performance to avoid the stomach issues that derail long runs. Do not forget carb loading before race day for marathons and longer events.

Your hydration strategy should be data-driven. calculate your sweat rate here to understand your individual fluid loss, and read about dual-carbohydrate transporters to see why maltodextrin plus fructose outperforms single-source carbs. Then build the session-by-session plan with the Fuelling Strategy Engine, read the full marathon fuelling plan if 42.2 km is the goal, and see endurance fuel for runners for how the range fits training weeks. Strength and hill blocks pair well with HYDRAX CREATINE, while single-serve sachets slot into a race vest without carrying a full pouch. When you are set, build your race kit.

The engine is the same for every mode: time equals distance divided by pace, summed across legs. In Triathlon mode you input swim distance and pace, bike distance and speed, run distance and pace, plus T1 and T2 transitions. The calculator adds them up. In Running and Cycling modes you supply the single leg.

Switch to Required pace for target and the engine works in reverse: enter your goal finish time and it tells you the pace you need to hold. For triathlon, it assumes your swim, bike, and transitions stay as entered and solves for the required run pace.

Pace and distance can be entered in any units (km/mi, m/yd, /100m or /100yd, km/h or mph). Conversion is handled automatically.