Half Marathon Time Calculator

Half Marathon Time Calculator

Predict your 13.1-mile finish time based on your running pace.

Minutes per Mile (min/mi) Minutes per Kilometer (min/km)

Your Estimated Finish Time:

00:00:00

How to Use the Half Marathon Time Calculator

Planning your first 13.1-mile race or aiming for a new Personal Best (PB)? Our Half Marathon Time Calculator helps you translate your training pace into a race-day reality. A half marathon consists of exactly 13.1094 miles or 21.0975 kilometers.

Understanding the Math

The calculator takes your average pace (the time it takes to run one mile or one kilometer) and multiplies it by the total race distance. For example, if you run at an 8:00 minute per mile pace:

  • Total Miles: 13.11 (rounded)
  • Calculation: 8 minutes × 13.11 = 104.88 minutes
  • Result: 1 hour, 44 minutes, and 53 seconds

Half Marathon Pace Chart (Target Times)

Pace (min/mi) Finish Time
7:001:31:44
8:001:44:50
9:001:57:56
10:002:11:03
11:002:24:09

Strategies for Your Best 13.1

To achieve your target time, consider these three factors:

  1. The Taper: Reduce your mileage 2 weeks before the race to ensure your legs are fresh.
  2. Pacing: Avoid starting too fast. Many runners lose time in the final 3 miles because they "burned out" in the first 3.
  3. Nutrition: Practice your hydration and gel intake during your long training runs to avoid stomach issues on race day.
function calculateRaceTime() { var pMin = document.getElementById("paceMin").value; var pSec = document.getElementById("paceSec").value; var unit = document.getElementById("paceUnit").value; // Default to 0 if empty var mins = parseFloat(pMin) || 0; var secs = parseFloat(pSec) || 0; if (mins === 0 && secs === 0) { alert("Please enter a valid pace."); return; } // Convert pace to total seconds per unit var totalSecondsPerUnit = (mins * 60) + secs; var distance = 0; var unitLabel = ""; if (unit === "mile") { distance = 13.1094; unitLabel = "miles"; } else { distance = 21.0975; unitLabel = "kilometers"; } // Total seconds for the race var totalRaceSeconds = totalSecondsPerUnit * distance; // Convert back to HH:MM:SS var hours = Math.floor(totalRaceSeconds / 3600); var remainingSeconds = totalRaceSeconds % 3600; var minutes = Math.floor(remainingSeconds / 60); var seconds = Math.floor(remainingSeconds % 60); // Formatting with leading zeros var displayHours = hours.toString(); var displayMinutes = minutes < 10 ? "0" + minutes : minutes; var displaySeconds = seconds < 10 ? "0" + seconds : seconds; var finalString = displayHours + ":" + displayMinutes + ":" + displaySeconds; document.getElementById("finalTime").innerHTML = finalString; document.getElementById("details").innerHTML = "Based on a pace of " + mins + "m " + secs + "s per " + (unit === "mile" ? "mile" : "km") + " over " + distance.toFixed(2) + " " + unitLabel + "."; document.getElementById("resultsArea").style.display = "block"; // Scroll to result document.getElementById("resultsArea").scrollIntoView({ behavior: 'smooth', block: 'nearest' }); }

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