Half Marathon Pace Calculator: Min per Mile

This calculator works out your average pace for a half marathon (13.1 miles) from a finish time, or estimates a finish time from a target pace. You enter a time and distance, and it returns your average pace in minutes per mile and your average speed in miles per hour, plus the same values in kilometers. The first result shown is your pace in minutes per mile, which is the number most half marathon runners track.

Formula

The core formula is simple: pace = total time ÷ distance. In symbols, P = T / D, where P is the average pace in minutes per mile, T is the total finish time in minutes, and D is the race distance in miles (13.1 for a half marathon). To get speed in miles per hour, use S = D / (T / 60), since you divide the distance by the time in hours. For metric values, multiply the pace in min/mile by 0.621371 to get min/km, and divide the speed in mph by 0.621371 (or multiply by 1.60934) to get km/h.

Worked Example

Using the default values: a finish time of 120 minutes (2:00:00) and a distance of 13.1 miles.

• Pace = 120 ÷ 13.1 = 9.1603 minutes per mile, which rounds to 9.16 min/mile (about 9:10 per mile).
• Speed = 13.1 ÷ (120 ÷ 60) = 13.1 ÷ 2 = 6.55 mph.
• Pace in min/km = 9.1603 × 0.621371 = 5.69 min/km (about 5:41 per km).
• Speed in km/h = 6.55 × 1.60934 = 10.54 km/h.

These match the calculator’s outputs for the defaults.

Why Your Half Marathon Pace Matters

Your average pace tells you how fast you actually ran, which is different from your instantaneous speed. A half marathon is 13.1 miles (21.0975 km), so even a small pace difference adds up. For example, running 9:00 per mile gives a finish time of about 1:57:54, while 10:00 per mile gives 2:11:00. Knowing your target pace helps you plan your effort, choose the right pace group, and avoid starting too fast—a common mistake that leads to a late-race fade.

How to Use the Calculator for Training

You can use this tool in two main ways:

• Goal pace: Enter your target finish time (e.g., 1:45:00 = 105 minutes) and see what pace you need to hold. For 1:45, the pace is 105 ÷ 13.1 = 8.02 min/mile (about 8:01).
• Pace validation: After a training run of any distance, enter the time and distance to see your current fitness level. If you ran 6 miles in 54 minutes, your pace is 9:00 per mile, which projects to a 1:57:54 half.

For training, many runners use pace zones: easy runs are typically 60–70% of max effort (about 1–2 minutes per mile slower than race pace), while tempo runs are near threshold (about 20–30 seconds per mile slower than 10K pace). This calculator gives you the numbers to set those zones.

Common Mistakes and How to Avoid Them

The most frequent error is mixing up units. If you enter a distance in kilometers but the calculator expects miles, your pace will be wildly off. Always check the unit labels. Another mistake is using a finish time that includes seconds without converting them. For example, 1:45:30 is 105.5 minutes, not 105.30. Also, remember that the pace is an average—it doesn’t account for hills, wind, or your own surges. A hilly course will have a slower average pace than a flat one, even with the same effort.

Pace Comparisons: What Do Different Times Mean?

Here are some common half marathon finish times and their average paces:

• 1:30:00 → 6.87 min/mile (about 6:52) – a fast, competitive time for most age groups.
• 1:45:00 → 8.02 min/mile (about 8:01) – a solid goal for many recreational runners.
• 2:00:00 → 9.16 min/mile (about 9:10) – a common first-time target.
• 2:15:00 → 10.31 min/mile (about 10:18) – a comfortable pace for newer runners.

These are just averages; your own target should reflect your fitness, training, and the course profile.

Limitations of the Formula

The pace formula assumes a perfectly even effort and flat course. In reality, you’ll run faster downhill and slower uphill. It also doesn’t account for weather, hydration, or fatigue. For race-day planning, add a buffer of 5–10 seconds per mile if you expect hills or heat. The formula is precise for what it does—converting time and distance—but it’s not a predictor of your ability. Use it as a planning tool, not a guarantee.

Frequently Asked Questions

How do I convert my pace from min/mile to min/km?
Multiply the min/mile pace by 0.621371. For example, 9:00 per mile is 9 × 0.621371 = 5.59 min/km (about 5:35). The calculator does this for you.

What is a good half marathon time for a beginner?
There’s no single answer, but many beginners aim for 2:00 to 2:30. A 2:15 finish is a 10:18 per mile pace. Focus on finishing comfortably rather than hitting a specific number.

Can I use this calculator for a 10K or full marathon?
Yes, if you change the distance. For a 10K, enter 6.2 miles; for a marathon, enter 26.2. The formula works for any distance, but the pace you can hold will differ.

How do I calculate my finish time from a pace?
Multiply your pace (in minutes per mile) by the distance. For example, 9.5 min/mile × 13.1 miles = 124.45 minutes, which is 2:04:27. You can also enter your pace as the time and 1 mile as the distance to see the pace, then multiply.

Why is the half marathon distance 13.1 miles?
The half marathon is exactly half of a full marathon, which is 26.2 miles (42.195 km). The official half marathon distance is 21.0975 km, which is 13.1094 miles, but it’s universally rounded to 13.1.

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in t | Finish time | min | 120 | 0
in d | Distance | miles | 13.1 | 0
out pace | Average pace | min/mile | t / d | 2
out speed | Average speed | mph | d / (t / 60) | 2
out pace_km | Pace (km) | min/km | (t / d) * 0.621371 | 2
out speed_km | Speed (km) | km/h | (d / (t / 60)) * 1.60934 | 2