Half Marathon Distance | 21.1 km & 13.1 Miles Explained

Half Marathon Distance

A half marathon is one of the most popular road race distances in the world. This page explains the official half marathon distance in kilometres and miles, plus quick reference conversions and common training run distances runners use to prepare.

✅ Official Half Marathon Distance

  • 21.0975 kilometres (usually rounded to 21.1 km)
  • 13.1094 miles (commonly rounded to 13.1 miles)

In everyday running and race listings, you’ll almost always see the half marathon distance written as 21.1 km or 13.1 miles.

Half Marathon Distance Conversions

Kilometres to Miles

  • 21.1 km ≈ 13.1 miles
  • 21 km ≈ 13.05 miles
  • 20 km ≈ 12.43 miles

Miles to Kilometres

  • 13.1 miles ≈ 21.1 km
  • 13 miles ≈ 20.92 km
  • 12 miles ≈ 19.31 km

How Long Does a Half Marathon Take?

Finish times vary widely based on fitness, experience, and course conditions. Here’s a simple way to estimate your half marathon finish time:

  • Time = Pace × Distance
  • Distance is 21.1 km or 13.1 miles

Example: If you run 6:00 min/km, then 21.1 km takes about 2 hours 06 minutes (approx).

Common Training Distances for Half Marathon Prep

Training plans vary, but many runners build up gradually with a mix of easy runs, long runs, and faster sessions. Common long-run distances used in half marathon training include:

  • 10 km (early base building)
  • 12–15 km (endurance build)
  • 16–18 km (peak long runs for many plans)
  • 19–22 km (some plans include a long run at/near race distance)

Half Marathon vs Marathon

  • Half marathon: 21.0975 km (13.1094 miles)
  • Marathon: 42.195 km (26.219 miles)

A half marathon is exactly half the distance of a full marathon.

Quick Reference

  • Half marathon distance: 21.1 km / 13.1 miles
  • Official exact distance: 21.0975 km / 13.1094 miles
  • Common label: “13.1” or “21.1K”

Disclaimer: This page is provided for general informational purposes only. Distances shown are based on standard race measurement conventions and are rounded for readability. Individual events may include minor course variations or measurement updates. Always refer to the official race organiser for the authoritative course distance and event details. This content is not affiliated with, endorsed by, or produced in association with any race organiser or governing body. We make no warranties regarding accuracy, completeness, or suitability for any purpose and accept no liability for any decision, interpretation, loss, or outcome based on this information.