Running Pace Calculator
Pace per mile and km, speed, and Riegel race predictions for 5K through marathon — from any distance and finish time.
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Enter time as 27:30 or 4:05:30
Pace, Speed and What They Predict
Pace = time ÷ distance: a 27:30 5K is 5:30/km (8:51/mile). The tool converts both ways and adds Riegel race predictions — the well-tested formula T₂ = T₁ × (D₂/D₁)¹·⁰⁶, which says you slow ~6% per doubling of distance. That 27:30 5K projects roughly a 57:20 10K and a 4:28 marathon (with proper training volume for the distance).
Predictions assume you are trained for the target distance — a fast 5K does not carry a marathon without the mileage. Race-day pacing wisdom: run the first half at predicted pace or a touch slower; banking time early is the classic way to blow up late.
Frequently Asked Questions
How accurate is the Riegel prediction?
Within a few percent for trained runners between 5K and marathon. It drifts optimistic for the marathon if weekly mileage is low, and pessimistic for pure speedsters at short distances.
What pace do I need for a sub-4 marathon?
5:41/km (9:09/mile) — enter 42.195 km and 4:00:00 to see it. Even splits or a slight negative split execute it best.
Treadmill pace vs road pace?
A 1% incline on the treadmill approximates outdoor effort at most training speeds; flat treadmill running reads slightly easier than road.
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Running Pace Calculator