Marathon Pace Calculator

Pacing a marathon

A marathon (26.21875 miles / 42.195 km) punishes an aggressive start more than any shorter race, since glycogen stores and muscular fatigue both become limiting factors in the last 6 to 10 miles.

This calculator supports both an even-split plan and a mild negative split (roughly 2% faster in the second half), a strategy many experienced marathoners use to bank fewer risky early minutes while still targeting the same finish time.

Check your 20-mile split against your watch during the race — it's typically the point where an overly ambitious pace starts to show.

Where these numbers come from

The formulas and default values in this calculator are based on:

• Official marathon race distance (26.21875 miles / 42.195 km)

These are planning estimates for training purposes. Check with a coach, trainer, or physician before starting a new program or maxing out.