Half Marathon Pace Calculator
Calculate your target half marathon running pace per km and per mile, and 5K, 10K, and 15K checkpoint split targets.
Calculate Half Marathon Target Pace (P_Half = Target_Time / 21.0975 km)
Enter your physical parameters below to compute verified half marathon pace metrics.
Calculation Results
Calculated using verified physical methodology: Half Marathon Target Pace: P_{\text{Half}} = \frac{T_{\text{seconds}}}{21.0975\text{ km}}
\text{10K Checkpoint Split: } T_{10\text{K}} = 10.0 \times P_{\text{Half}}
Quick Summary
The Half Marathon Pace Calculator evaluates target running pace per kilometer ($P_{\text{Half}} = \frac{T_{\text{Half}}}{21.0975}$), pace per mile, 5K, 10K, and 15K checkpoint targets for sub-1:30, sub-1:45, and sub-2:00 half marathon race goals.
Formula Explanation
Half Marathon Target Pace: P_{\text{Half}} = \frac{T_{\text{seconds}}}{21.0975\text{ km}}
\text{10K Checkpoint Split: } T_{10\text{K}} = 10.0 \times P_{\text{Half}}
How It Works
The Half Marathon Pace Calculator converts target finish time to total seconds ($T$). It divides total seconds by $21.0975\text{ km}$ ($13.10938\text{ miles}$) to compute target pace per km (`min:sec/km`) and pace per mile (`min:sec/mi`). It projects checkpoint split times at 5K, 10K, 15K, and 20K.
Step-by-Step Worked Example
Practical Problem: Calculate target half marathon running pace per kilometer, per mile, average speed, and 10K checkpoint split time to achieve a **Sub-1:45 Half Marathon** finish time ($1\text{ hr } 45\text{ min } 00\text{ sec}$).
- Step 1: Identify Input Parameters: Target Time $T = 1\text{ hr } 45\text{ min } 00\text{ sec} = 6,300\text{ seconds}$, Distance $d = 21.0975\text{ km}$.
- Step 2: Calculate Kilometer Pace ($P_{\text{km}} = 6300 / 21.0975$): $P_{\text{km}} = \frac{6,300}{21.0975} = 298.61\text{ seconds/km} = \mathbf{4:59\text{ min/km}}$.
- Step 3: Calculate Mile Pace ($6300 / 13.10938$): $P_{\text{mile}} = \frac{6,300}{13.10938} = 480.57\text{ seconds/mile} = \mathbf{8:01\text{ min/mile}}$.
- Step 4: Calculate Average Running Speed: Speed $= \frac{21.0975\text{ km}}{1.75\text{ hr}} = \mathbf{12.06\text{ km/h}} = \mathbf{7.49\text{ mph}}$.
- Step 5: Calculate 10K Checkpoint Split ($10.0 \times 298.61$): $2,986\text{ seconds} = \mathbf{49\text{ min } 46\text{ sec at 10K mat}}$.
Real-World Calculation Examples
Scenario 1: Sub-1:30 Half Marathon Target (1h 30m 00s)
Parameters: Target Time = 1h 30m 00s
Result: Pace = **4:16 /km** ($6:52\text{ /mile}$, 14.07 km/h, 42:39 10K split). Competitive half marathon.
Scenario 2: Sub-1:45 Half Marathon Target (1h 45m 00s)
Parameters: Target Time = 1h 45m 00s
Result: Pace = **4:59 /km** ($8:01\text{ /mile}$, 12.06 km/h, 49:46 10K split). Popular club goal.
Scenario 3: Sub-2:00 Half Marathon Target (2h 00m 00s)
Parameters: Target Time = 2h 00m 00s
Result: Pace = **5:41 /km** ($9:09\text{ /mile}$, 10.55 km/h, 56:53 10K split). Landmark runner milestone.
Scenario 4: World Record Half Marathon Pace (57m 31s)
Parameters: Target Time = 0h 57m 31s
Result: Pace = **2:44 /km** ($4:23\text{ /mile}$, 21.99 km/h, 27:16 10K split). Jacob Kiplimo world record.
Key Benefits of Using This Calculator
Intermediate Checkpoint Splits
Calculates exact split target times for 5K, 10K, 15K, and 20K timing mats during the race.
Lactate Threshold Pacing
Helps runners set pace targets right around lactate threshold (LT2) for optimal 21.1K performance.
Multi-Unit Readouts
Outputs kilometer pace, mile pace, speed in km/h & mph, and split times.
100% Free & Client-Side
Executes locally in your browser with zero latency or web server transmission.
Frequently Asked Questions (FAQ)
What is a half marathon race distance?
A half marathon is exactly 21.0975 kilometers or 13.10938 miles (52.74 laps of a standard 400m outdoor track).
What pace is required for a sub-2 hour half marathon?
5:41 min/km (9:09 min/mile or 10.55 km/h average speed).
What pace is required for a sub-1:45 half marathon?
4:59 min/km (8:01 min/mile or 12.06 km/h average speed).
What pace is required for a sub-1:30 half marathon?
4:16 min/km (6:52 min/mile or 14.07 km/h average speed).
How many miles is a half marathon?
A half marathon is 13.10938 miles (commonly rounded to 13.1 miles).
What is average half marathon finish time for men and women?
Average male half marathon finish time is ~1:55 to 2:05; average female half marathon finish time is ~2:10 to 2:22.
What key workout builds half marathon endurance?
Long tempo runs of 12-16 km at goal half marathon pace, or 3x5 km threshold blocks.
Do half marathons require carb loading?
Modest carbohydrate loading 24-36 hours prior helps maximize muscle glycogen stores for runs exceeding 90 minutes.
What is negative splitting in a half marathon?
Negative splitting is running the first 10K slightly conservative (e.g. 5:05 /km) and the second 11.1K faster (e.g. 4:55 /km).
Who holds the world half marathon record?
Jacob Kiplimo (Men: 57:31) and Letesenbet Gidey (Women: 1:02:52).