About PaceLab
Fast, free running calculators with math you can check, and no strings attached.
What this site is
PaceLab (at paceslab.com) is a small collection of running calculators: a pace calculator, a race time predictor, a splits calculator, a treadmill converter and pace charts for the 5K, 10K, half marathon and marathon. Each tool does one job, loads instantly and works on any device.
The principles
Every calculation runs client-side in your browser, so your training data never leaves the tab. The math is standard and transparent: pace equals time divided by distance, miles convert at exactly 1.609344 km, and race predictions use Riegel's well-known formula with the 1.06 exponent. If a number ever looks off, you can verify it by hand.
There are no accounts, no paywalls and no dark patterns. See the privacy policy for the details on data handling.
Start here
Most runners want the running pace calculator first. If you are planning a race, pair the predictor with the splits calculator to turn a recent result into a concrete pacing plan.