Half Marathon Pace Calculator
Training for a Half Marathon? Get your splits and target pace instantly. Whether you want to break 2 hours or 90 minutes, we have the math covered.
Common Race Pace Chart
| Time | Pace (min/km) | Pace (min/mi) |
|---|---|---|
| Marathon Sub-3 | 4:16 | 6:52 |
| Marathon Sub-3:30 | 4:58 | 8:00 |
| Marathon Sub-4 | 5:41 | 9:09 |
| Half Sub-1:30 | 4:15 | 6:51 |
| Half Sub-2:00 | 5:41 | 9:09 |
| 10K Sub-40 | 4:00 | 6:26 |
| 5K Sub-20 | 4:00 | 6:26 |
Specialized Versions
Scientific Methodology & Accuracy
Our tools are built using peer-reviewed research and industry-standard formulas. This specific calculator utilizes PACE CALCULATOR metrics validated by sports science organizations like the ACSM and NSCA.
The concept of 'Critical Power' serves as a more stable anchor for training than the traditional FTP.
Performance Concept
"Precision metrics are the secret weapon of the world's most successful endurance athletes."
Expert Protocol
"Supplementation should only be considered once your base nutrition and sleep are optimized. Individual physiology varies. Use these results as a baseline and adjust based on your personal feel."
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How to Use This Tool
- 1
Enter your goal race distance and target finish time into the Half Marathon Pace Calculator.
- 2
Review the calculated pace per kilometer and per mile to confirm it aligns with your current training capacity.
- 3
Cross-reference with your recent long run pace. If the target is 15+ sec/km faster, build gradually over 8–12 weeks.
- 4
During your next marathon-pace (MP) workout, use this pace to build neuromuscular memory for race day execution.
Key Terminology
Frequently Asked Questions
Q1 What pace do I need to run a sub-3 hour marathon?
You need to maintain an average pace of 4:16 per kilometer (6:52 per mile) for the entire 42.195km. This requires a VO2 Max of approximately 52–55 ml/kg/min and significant marathon-specific training.
Q2 How does temperature affect my running pace?
Performance declines by approximately 60 seconds per hour for every 5°C above an optimal racing temperature of 10–12°C. Racing in 25°C? Add 90–120 seconds to your per-kilometer pace compared to a cool day.
Q3 What is the 10% rule for increasing mileage?
Never increase your weekly running mileage by more than 10% from one week to the next. This prevents the accumulation of training stress that leads to overuse injuries like shin splints and stress fractures.
Q4 What is negative splitting and why does it matter?
Negative splitting means running the second half of a race faster than the first half. It is the pacing strategy used in virtually every marathon world record because it conserves glycogen early and maximizes performance in the final 10km.
What Pace Do You Need for Your Half Marathon Goal?
Your required half marathon pace = goal time ÷ 21.0975. A sub-2:00 goal requires 5:41 per km (9:09 per mile). A sub-1:30 goal requires 4:16 per km (6:52 per mile). Enter your target time above for exact splits.
The Half Marathon: Physiology and Strategy
The Half Marathon (21.1 km / 13.1 miles) is the fastest-growing race distance globally. It sits at the intersection of speed and endurance: unlike the 5K or 10K, which are near-VO2 Max efforts, the half marathon is raced at or slightly below the lactate threshold — the highest intensity at which lactate clearance keeps pace with production.
Race pace feels "comfortably hard." You can say a few words but cannot sustain conversation. It is the same intensity as an all-out 1-hour effort. Both your aerobic base and your lactate threshold are primary limiters — which means training must address both.
Half Marathon Pace Chart
| Goal Time | Pace (min/km) | Pace (min/mi) | 5K Split | 10K Split | Equivalent 5K Time |
|---|---|---|---|---|---|
| Sub 1:20 | 3:47 | 6:06 | 18:55 | 37:50 | ~17:30 |
| Sub 1:25 | 4:02 | 6:29 | 20:10 | 40:20 | ~19:00 |
| Sub 1:30 | 4:16 | 6:52 | 21:20 | 42:40 | ~20:00 |
| Sub 1:45 | 4:58 | 7:59 | 24:50 | 49:40 | ~23:00 |
| Sub 2:00 | 5:41 | 9:09 | 28:25 | 56:50 | ~26:30 |
| Sub 2:15 | 6:24 | 10:18 | 32:00 | 1:04:00 | ~29:30 |
| Sub 2:30 | 7:06 | 11:26 | 35:30 | 1:11:00 | ~33:00 |
Required Fitness for Each Goal
| Goal Time | Recommended 10K Time | Peak Weekly Volume | Training Duration |
|---|---|---|---|
| Sub 1:25 | Under 38:00 | 70–90 km/week | 14–18 weeks |
| Sub 1:30 | Under 42:00 | 60–75 km/week | 12–16 weeks |
| Sub 1:45 | Under 48:00 | 45–60 km/week | 12–14 weeks |
| Sub 2:00 | Under 55:00 | 35–50 km/week | 12 weeks |
| First finish | Any | 25–40 km/week | 10–12 weeks |
Key Training Runs for the Half Marathon
1. Threshold Runs (Weekly) 30–40 minutes at half marathon goal pace, or slightly faster. Raises your lactate threshold — the primary performance limiter at this distance. Practical example: 3 × 10 minutes at HM goal pace, 2-minute jog recovery between reps.
2. Long Runs (Weekly) Build to 19–22 km at easy pace (60–75 sec/km slower than goal pace). Develops aerobic base and fat oxidation capacity without the recovery cost of race-pace long runs. The long run is non-negotiable — it is the foundation of half marathon fitness.
3. Race-Pace Miles (Every 10–14 Days) 4–6 × 1 mile at exact goal half marathon pace, 90-second rest. Builds the muscular and metabolic memory of holding goal effort on fatigued legs. This is more specific than threshold work and more recoverable than VO2 Max intervals.
4. VO2 Max Intervals (Optional, for sub-1:45 athletes) 5 × 800m or 4 × 1000m at 5K race pace, 90-second rest. Raises the aerobic ceiling. Most impactful for runners whose 5K time suggests they should be running faster half marathons than they currently do.
*Source: Pfitzinger, P. & Douglas, S. (2016). Road Racing for Serious Runners. Human Kinetics.*
Race-Day Pacing Strategy
Research on recreational half marathon pacing (Renfree & Gibson, 2013, *International Journal of Sports Physiology and Performance*) consistently shows that even splits or a slight negative split produce the fastest times. Going out 5–10 seconds/km too fast in the first 5 km nearly always degrades the final 5 km, eroding the early time advantage.
Recommended execution: - Km 1–5: Run 3–5 seconds/km *slower* than goal pace. Let the adrenaline crowd pass. - Km 5–16: Lock into exact goal pace. This is the race. - Final 5 km: Run by feel. If you have energy remaining, accelerate gradually — this is where patient pacing pays off.
The critical checkpoint: cross 10 km at exactly half your goal time ± 20 seconds. Any faster is a warning sign.
Race-Day Variables
| Variable | Estimated Impact on Finish Time |
|---|---|
| Heat above 20°C (68°F) | +30–90 sec/km above threshold |
| Humidity above 75% | +1–3 min total |
| Net elevation gain >100m | +2–5 min total |
| Wind above 20 km/h (headwind) | +15–45 sec per exposed km |
*Source: Ely, M.R. et al. (2007). Aerobic performance is degraded despite modest hyperthermia. Med Sci Sports Exerc, 39(5), 987–994.*
Frequently Asked Questions
What is a good half marathon time for a beginner? For first-time half marathoners, finishing between 2:00–2:30 is a solid target. Sub-2:00 is an excellent goal once you have completed at least one half marathon and have a consistent 40+ km/week training base.
How should I fuel during a half marathon? At race pace, most runners need 1–2 gels (22–25g carbs each) for races over 90 minutes. Take your first gel at km 6–8 with water, and a second at km 13–14 if needed. For sub-1:30 athletes, fueling is often not necessary but electrolytes can help.
Can I run a half marathon on 3 runs per week? Yes, for finishing. For a specific time goal, 4–5 runs per week is significantly more effective. The minimum effective dose is: one long run (16–20 km), one threshold or quality session, one easy recovery run.
How do I predict my half marathon time from a 5K? Use Riegel's formula: HM time = 5K time × (21.0975 ÷ 5)^1.06. This gives a rough prediction assuming you have trained specifically for the half marathon distance. Without long-run training, most runners underperform this prediction by 5–10%.
Use Cases / Example Scenarios
Apply the output to find your lactate threshold pace and design progressive tempo sessions that build sustainable speed.
Input your goal finish time to calculate the exact fueling schedule (km 7, 14, 21, 28, 35) needed to avoid glycogen depletion.
When ambient temperature exceeds 15°C, use the calculated pace to apply a 60-sec/hour slowdown for realistic warm-weather goal-setting.
Enter your recent 5K or 10K result to project a realistic marathon or half marathon finish time using the Daniels VDOT method.
Confirm your target pace hasn't drifted during a 3-week taper by running a controlled 5km at goal pace with heart rate monitoring.
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