Half Marathon Pace Calculator – Plan Your 13.1 Mile Race
Calculate your required half marathon pace for any goal finish time. Get per-km, per-mile pace and mile-by-mile split times for your 13.1 mile race.
Half Marathon Pace Chart: Goal Times and Required Splits
The half marathon (21.0975 km / 13.1094 miles) is the world's fastest-growing race distance — balancing speed, endurance, and achievability. Whether chasing a PR or running your first 13.1, knowing your required pace is essential for race day success.
| Goal Time | Pace /km | Pace /mile | 10K Split |
|---|---|---|---|
| 1:25:00 | 4:02 | 6:29 | 40:20 |
| 1:30:00 | 4:16 | 6:52 | 42:40 |
| 1:35:00 | 4:30 | 7:15 | 45:00 |
| 1:40:00 | 4:44 | 7:37 | 47:20 |
| 1:45:00 | 4:58 | 8:00 | 49:40 |
| 1:50:00 | 5:12 | 8:22 | 52:00 |
| 2:00:00 | 5:41 | 9:09 | 56:50 |
| 2:10:00 | 6:09 | 9:55 | 61:30 |
| 2:20:00 | 6:38 | 10:40 | 66:20 |
| 2:30:00 | 7:06 | 11:27 | 71:00 |
| 3:00:00 | 8:31 | 13:44 | 85:10 |
Half Marathon Pacing Strategy: 3-Phase Approach
The half marathon sits at a physiological crossroads — long enough to demand glycogen management, short enough that aerobic capacity is the primary limiter. The optimal race strategy:
- Miles 1–4 (conservative): Run 5–10 seconds per km slower than goal pace. Race adrenaline and fresh legs will make this feel too easy — that's intentional. You're banking aerobic capacity.
- Miles 5–10 (steady): Settle into goal pace. Check your 10K split — it should be within 15 seconds of target. Heart rate should be 82–87% of max.
- Miles 11–13.1 (finish): Increase effort. If paced correctly, you'll have genuine reserves. Running the final 5K faster than the opening 5K is the hallmark of excellent pacing.
Research published in the Journal of Strength and Conditioning Research found that recreational runners who ran even or negative splits finished an average of 8.4 minutes faster than those with significant positive splits at equivalent fitness levels.
Half marathon pace corresponds to approximately 85–90% of VO2max for trained runners — that means it should feel hard, not comfortable. Your first mile feeling genuinely controlled (not easy) is the correct target.
Training Paces for Half Marathon Preparation
Based on Jack Daniels VDOT system, training paces for common half marathon goal times:
| HM Goal | Easy /km | Tempo /km | Interval /km |
|---|---|---|---|
| 1:30 | 5:00–5:30 | 4:00–4:05 | 3:35–3:40 |
| 1:45 | 5:30–6:05 | 4:35–4:40 | 4:05–4:10 |
| 2:00 | 6:05–6:40 | 5:10–5:15 | 4:35–4:40 |
| 2:15 | 6:35–7:15 | 5:45–5:50 | 5:05–5:10 |
| 2:30 | 7:10–7:50 | 6:18–6:25 | 5:35–5:45 |
Key workouts for half marathon fitness:
- Tempo runs: 20–40 minutes at threshold pace — the most effective single workout for improving lactate threshold and half marathon performance.
- Half-marathon pace intervals: 3–5 × 2 miles at goal HM pace with 90-second recovery. Teaches legs to operate at race pace.
- Long runs: 16–20 km at easy pace, building to 21–23 km in peak weeks. Develops the aerobic base that supports race pace.
Fueling and Hydration for the Half Marathon
Unlike the full marathon, glycogen depletion is rarely the limiting factor in a half marathon for trained runners — you begin with enough stored glycogen to run approximately 20 miles at race effort. However, hydration and pacing errors are common causes of poor half marathon performances.
Fueling strategy by finish time:
- Under 1:45: Water at aid stations is sufficient for most runners. Optional: one gel at mile 7–8 for performance without GI risk.
- 1:45–2:15: Recommend 1–2 gels. Take first fuel at mile 6–7, second at mile 10–11.
- Over 2:15: Treat more like a marathon. Plan for 2–3 gels or consistent sports drink intake.
Hydration: drink 150–250ml at each aid station, starting from mile 3–4. Don't skip early aid stations because you feel fine — dehydration is cumulative. Pre-race meal: familiar carbohydrate-based meal 2–3 hours before start. Avoid high-fat, high-fiber foods that slow gastric emptying.
Predicting Your Half Marathon Time
The best predictor of your half marathon time is a recent race performance. Riegel's formula: T2 = T1 × (D2/D1)^1.06. Common predictors:
| Known Performance | Predicted Half Marathon |
|---|---|
| 5K in 20:00 | ~1:32:30 |
| 5K in 22:00 | ~1:41:00 |
| 5K in 25:00 | ~1:55:00 |
| 5K in 28:00 | ~2:08:30 |
| 10K in 45:00 | ~1:39:00 |
| 10K in 50:00 | ~1:50:00 |
| 10K in 55:00 | ~2:01:00 |
| 10K in 60:00 | ~2:12:00 |
These predictions assume equal preparation for both distances. If training specifically for the half, the prediction will be accurate. If only doing short races, add 2–5 minutes. In hot weather or on hilly courses, add additional time.
Recovery After a Half Marathon
The half marathon is a serious physiological stressor even though it's only half the marathon distance. Appropriate recovery protects long-term training continuity and prevents overtraining.
Recovery timeline:
- Days 0–1: Easy walking only. Focus on nutrition: 1.2–1.6g protein/kg body weight, carbohydrate repletion, hydration. Expect muscle soreness especially in quads and calves.
- Days 2–3: Light movement — 20–30 min easy walk or very easy jog. Foam rolling, stretching. Sleep is the most powerful recovery tool.
- Days 4–5: Easy running 30–45 minutes if soreness has resolved. Keep heart rate in Zone 1–2.
- Day 7+: Return to structured training. Most runners are fully recovered by 7–10 days post-half marathon.
General rule: take 1 easy day for every 1.5–2 miles raced before returning to hard training — that's 9–14 days of easy running before your next quality session after a half marathon.
"The half marathon demands sustained effort near or at the lactate threshold — approximately 85–92% of VO2max for trained runners. Optimal training combines threshold sessions, long runs, and race-specific pacing work to develop the physiological and psychological resilience needed for this distance."
💡 Did you know?
- The half marathon is the world's fastest-growing race distance — over 8,000 half marathons are held globally each year, with more than 2 million finishers in the US alone.
- The IAAF did not recognize the half marathon as an official world record distance until 1994.
- The men's world record for the half marathon is 57:30 (Jacob Kiplimo, Uganda, 2021) — a pace of 2:44 per kilometer.
Frequently Asked Questions
What pace do I need to run a sub-2 hour half marathon?
To break 2 hours in a half marathon, you need an average pace of 5:41 per kilometer or 9:09 per mile. At the 10K mark, your split should be around 56:50. This requires a 5K time of approximately 26–27 minutes as a minimum fitness indicator.
Is a 1:45 half marathon good?
A 1:45 half marathon (4:58/km, 8:00/mile) is an excellent time for recreational runners — placing you in the top 25–30% at most mass-participation half marathons. It requires genuine training and corresponds to a VDOT of approximately 46–48.
How long does it take to prepare for a first half marathon?
For a complete beginner, allow 12–20 weeks to build from running 3 km comfortably to completing a half marathon. For someone with a 15–25 km/week base, 10–12 weeks is typically sufficient.
What should I eat before a half marathon?
Eat a familiar, carbohydrate-focused meal 2–3 hours before start. Good options: oatmeal with banana, toast with peanut butter and honey, or a bagel. Aim for 400–700 calories. Test your race-day breakfast during long training runs.
How is half marathon pace different from marathon pace?
Half marathon pace is typically 15–30 seconds per km faster than marathon pace. The effort level is higher — you're operating closer to lactate threshold throughout, whereas marathon pace is largely aerobic.
What heart rate should I run a half marathon at?
For most trained runners, half marathon pace corresponds to 83–88% of maximum heart rate — Zone 4 threshold level. If you don't know your max HR, use 220 minus age as a rough estimate, then target 83–88% of that number.
Should I take gels during a half marathon?
Depends on finish time. Runners under 1:45 can usually complete on glycogen alone. Runners taking 1:45–2:15 should take 1–2 gels. Those running 2:15+ should fuel similarly to a marathon with 2–3 gels. Always test gels in training first.
How many days should I rest after a half marathon?
Plan for 5–7 days of easy activity before returning to structured training. Most runners are fully recovered in 7–10 days. Take a full rest day on race day and the day after. The muscular damage extends well beyond when you stop feeling sore.