Running pace calculator

Pace is time divided by distance — how long each unit takes. Speed is its reciprocal. Runners use pace because it is what a watch shows and what you can hold in your head mid-race.

pace = time ÷ distance time = pace × distance speed = distance ÷ time

Marathon distance is oddly specific

42.195 km — 26 miles 385 yards — comes from the 1908 London Olympics, where the course was extended so the finish would sit in front of the royal box. The figure was standardised in 1921 and has been the distance ever since.

Negative splits

The even splits above are a planning tool, not a strategy. Most marathon personal bests are run with a slightly faster second half, because starting conservatively preserves glycogen. Going out fast and fading is the most common way a well-trained runner misses a target.

Predicting across distances

The table above assumes the same pace at every distance, which no runner achieves. Riegel's formula — T₂ = T₁ × (D₂/D₁)^1.06 — is the standard correction, and even it tends to be optimistic for the marathon unless your training volume supports it.