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RUNNER TOOLS

A small kit of calculators every runner ends up needing eventually. Everything runs in your browser — nothing gets stored, nothing gets sent anywhere.

Pace Calculator →

Distance, time, or pace — solve for whichever one you’re missing.

Give it any two of distance, time, and pace, and it works out the third. No sign-up, no ads, just the math.

Race Time Predictor →

Ran a 10K? See what that says about your marathon.

Enter a recent race result and get predicted finish times for 5K, 10K, half marathon, and marathon, using the Riegel formula.

Splits Calculator →

A goal time, broken into even splits per km or mile.

Pick a distance and a goal finish time, get a full split table — the pacing sheet you can screenshot before race day.

Training Paces →

One goal pace, five training paces.

Enter your goal race pace and get rough, ready-to-use ranges for easy, tempo, and interval efforts.

Heart Rate Zones →

Max HR and resting HR in, five zones out.

Karvonen-method heart rate zones — recovery through max effort — from your max and resting heart rate.

Race Countdown →

How many days until race day, exactly.

Pick a race date and get a live countdown — days, hours, and minutes to the start line.