How to Use the Half Marathon Pace Calculator
A half marathon covers 13.10937 miles (21.0975 km) — exactly half of a full marathon. Setting a goal finish time ahead of race day makes it much easier to plan your training paces. Enter your goal time (hours, minutes, seconds) and this calculator works out the per-mile and per-km pace you need to hold to hit that finish time.
Pace alone doesn't tell the whole story — pairing it with a split table for 5K, 10K, 15K, and 20K lets you check in real time during the race whether you're ahead of or behind your goal pace. Going out too fast in the first few miles is one of the most common reasons runners fade late, so consider setting your GPS watch to alert you at each split.
Setting an overly aggressive goal time can push your training intensity too high, so it's smart to base your target on a recent 10K or half marathon result rather than a number you simply hope for. A common rule of thumb is to multiply your recent 10K time by roughly 2.2-2.3 for a realistic half marathon goal.
Frequently Asked Questions
A half marathon is 13.10937 miles (21.0975 km), exactly half of a full marathon's 26.2 miles. This calculator uses that official distance for all pace and split calculations.
Per-mile pace is how long it takes to run one mile, while per-km pace is how long it takes to run one kilometer (about 0.62 miles). Checking both is handy if your GPS watch or a race abroad uses a different unit.