Half Marathon Pace Calculator

The official IAAF half-marathon distance is 21.0975 kilometers, which is exactly half of the full marathon's 42.195 km. Converted using the international mile (1 mile = 1.609344 km exactly), that comes out to 13.10937779 miles, which the calculator rounds to 13.10938 mi. The common shorthand 13.1 mi is the same number truncated to one decimal: it is short by 36 feet (about 11 meters) over the full race. For pace and split planning the difference is trivial (under 5 seconds at 8:00/mi pace), but the calculator uses the full 13.10938 figure so the final cumulative split time on the table matches your target finish to the second.

Sub-1:30 half: 6:52/mile or 4:16/km, average speed 8.74 mph. Sub-1:45 half: 8:00/mile or 4:58/km, 7.49 mph. Sub-2:00 half: 9:09/mile or 5:41/km, 6.55 mph. Sub-2:15 half: 10:18/mile or 6:24/km, 5.83 mph. Sub-2:30 half: 11:27/mile or 7:06/km, 5.24 mph. For context, the global median half-marathon finish has hovered around 1:58 for men and 2:11 for women in recent years (Running USA, RunRepeat), so a sub-2:00 puts you near or above the median. Use the splits-per-mile table to confirm what each mile marker on your watch should read at the target pace, and the splits-per-km table to cross-check at metric race signage.

The calculator uses five widely cited recreational bands. Elite is under 1:30:00 (top single-digit percent of fields). Competitive is 1:30:00 to 1:44:59 (strong age-group runners). Good is 1:45:00 to 1:59:59 (a well-trained hobby runner). Average is 2:00:00 to 2:30:00 (typical first-half-marathon territory; the global median sits inside this band). Recreational is anything over 2:30:00 (often run-walk pace, ideal for first-timers and walkers). These are heuristics, not absolute standards: a 2:00 finish in a flat road race differs from a 2:00 finish on a hilly trail event, and age-graded performance tables (USATF Masters, WMA) are the right tool when you want apples-to-apples comparisons across age groups.

No. Boston qualifying standards require a certified finish at the full 42.195 km marathon distance. Half-marathon times are never accepted as direct qualifiers. This calculator predicts an equivalent marathon time with a half-to-full multiplier, then compares that projection with the 2027 open-age standards of 2:55:00 for men and 3:25:00 for women and nonbinary athletes. The actual qualification still requires a qualifying full-marathon result and depends on your age group and registration cutoff.

The calculator applies Pete Riegel's formula, T2 = T1 * (D2 / D1)^1.06. Doubling the distance gives 2^1.06 = 2.08493, so the projected marathon time is about 2.08493 times the half-marathon time. The estimate assumes comparable preparation and conditions. It is often optimistic when your training has not included marathon-specific weekly volume, long runs, pacing, and fueling.