Pace Calculator
Calculate running or walking pace, speed, and finish times for any distance.
About Pace Calculation
Pace is measured in minutes per kilometer or mile. Race predictions assume you can maintain the same pace, which is optimistic for longer distances. A general rule of thumb: marathon pace is about 5-8% slower than half marathon pace.
About This Tool
Computes pace (time per unit distance) and speed (distance per unit time) given any two of distance, time, and pace. Supported units: miles, kilometers, meters, yards. Output formats include min/mile, min/km, mph, and km/h.
Derived outputs include split times for common race distances (5K, 10K, half marathon, marathon) and projected finish times for goal paces. Conversion between pace and speed inverts the value: 6 min/mile equals 10 mph.
The mathematical relationships are straightforward but the physiology behind pacing is not. Pace is a flat metric; effort depends on grade, surface, weather, fitness state, and accumulated fatigue. A 7:00/mile on a flat track is a different effort from the same pace on rolling terrain or in 90°F humidity. Heart rate, perceived exertion, and (for runners with power meters) running power offer better effort proxies. The pace calculator handles the arithmetic; the runner handles the application.
Pace projection across distances follows non-linear patterns. Riegel's formula (T2 = T1 × (D2/D1)^1.06) provides reasonable estimates: a 20:00 5K projects to approximately 41:30 10K and 1:32 half-marathon. The 1.06 exponent reflects the fact that aerobic decay accelerates over longer distances; even-pace projections systematically overestimate marathon performance from short-distance times. VDOT tables (developed by Jack Daniels) provide finer-grained projections incorporating training adaptations.
A worked example: a runner targets a sub-3:30 marathon. 3:30:00 / 26.2 miles = 8:00.7/mile pace. Splits at goal pace: 5K in 24:51, 10K in 49:42, half in 1:44:50. Comparing this 8:00 pace to the runner's recent 5K time (say, 21:30 = 6:55/mile) using Riegel: the projected marathon from 21:30 5K is roughly 3:25, suggesting the goal is achievable with appropriate training. The projection assumes adequate aerobic base and marathon-specific preparation; without long runs in training, the marathon-from-5K formula systematically underdelivers.
Negative split pacing — running the second half faster than the first — produces faster finish times than even or positive splits in most race distances from 5K to marathon. Elite marathon performances commonly show negative splits of 30–90 seconds. The mechanism: starting conservative preserves glycogen and limits early lactate accumulation, allowing a sustained or accelerating effort in the back half. Positive splitting (going out fast) feels easier early but exacts disproportionate cost late.
Limitations: the calculator does not model environmental adjustments. Heat (above 60°F starts adding ~1% per 10°F to marathon time), humidity, altitude, and wind all shift achievable pace. Race-pace prediction tools that adjust for forecast conditions exist but require additional inputs. The basic calculator handles steady-state effort on neutral conditions; real-race execution requires reading the day.
The about text and FAQ on this page were drafted with AI assistance and reviewed by a member of the Coherence Daddy team before publishing. See our Content Policy for editorial standards.