Tools & Calculators
Free, pure client-side calculators built for runners. Calculate target split paces, build custom negative split charts, and predict finish times across all race distances.
Running Pace Calculator
Calculate target pace per km or mile, finish times, and running speeds. Generate custom split charts with even, negative (fast-finish), and positive pacing bands.
Race Time Predictor
Predict your target finish time across 5K, 10K, Half Marathon, and Full Marathon. Compare Pete Riegel’s fatigue formula, Jack Daniels’ VDOT oxygen cost model, or training pace.
Guides & Articles
Race-day checklist
Everything to do the night before, the morning of, and during the race, so the only surprise on the day is your finish time.
Running pace, explained
Pace is minutes per kilometer. Everything in running, from easy runs to race predictions, hangs off that one number.
How to pick your first marathon
Your first marathon is a 4 to 6 month commitment. Pick the race on cutoff time, season, course, and logistics, not on the medal photo.
The Complete Running Guide: From Couch to Marathon
Everything you need to know about running: why to do it, how to start, proper form, how much to run, training by distance, injury prevention, nutrition, and recovery.