Half Marathon Pace Calculator – Plan 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.

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:

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:

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.

Daniels' VDOT Approach to Half Marathon Racing

Jack Daniels' VDOT system provides one of the most scientifically rigorous frameworks for half marathon pace prescription. In Daniels' Running Formula, he argues that half marathon race pace falls between marathon pace (M) and threshold pace (T) for most runners — making it a uniquely demanding event that stresses both aerobic endurance and lactate clearance simultaneously.

Daniels' VDOT-based half marathon paces for common fitness levels:

A critical Daniels principle for half marathon racing: your training paces should be based on current VDOT, not goal VDOT. If your recent 10K predicts VDOT 45 but you want to race at VDOT 48, train at VDOT 45 paces and let fitness develop naturally. Training faster than your current capacity causes overtraining, not faster adaptation.

Daniels prescribes specific half marathon preparation workouts:

• T-pace cruise intervals: 3–4 × 10 minutes at threshold pace with 2-minute recovery. The sustained lactate clearance stimulus directly supports half marathon performance.
• M-to-T progression runs: 60–90 minute runs starting at marathon pace and progressing to threshold pace in the final 20–30 minutes. These teach the body to transition from comfortable to race effort.
• I-pace intervals: 5 × 1000m at interval pace (VO2 max effort) with 3-minute recovery. These raise the aerobic ceiling above half marathon race intensity.

Daniels emphasizes that the half marathon is the distance where threshold fitness matters most. A runner with a high lactate threshold relative to VO2 max will outperform a runner with a higher VO2 max but lower threshold at this distance every time.

Pfitzinger's Half Marathon Training Plans

Pete Pfitzinger's Faster Road Racing provides the most detailed half marathon-specific training plans available. His philosophy for the half marathon centers on three pillars: endurance, lactate threshold, and race-specific pace work.

Pfitzinger offers plans at multiple mileage levels (31–47, 47–63, and 63–84 miles per week), each spanning 12 weeks. Key features that distinguish his half marathon plans from generic programs:

• Tempo runs with a twist: Pfitzinger's tempo runs progress from 4 miles to 8–9 miles at lactate threshold pace over the 12-week plan. The final tempo runs approach race-like duration at race-like intensity — a powerful stimulus.
• V̇O2max intervals: Weekly VO2 max sessions (800m–1200m repeats at 3K–5K effort) maintain speed and raise the aerobic ceiling throughout the training block.
• Race-pace long runs: The final 4–6 miles of weekend long runs (15–17 miles total) are run at goal half marathon pace. This teaches the body to produce race effort on glycogen-depleted legs.
• General aerobic (GA) runs: Mid-week steady runs at a pace between easy and marathon effort. These build aerobic capacity without the recovery cost of quality sessions.

Pfitzinger's unique contribution to half marathon training is the concept of lactate threshold progression — systematically increasing both the duration and intensity of threshold work across the training cycle. By the final 3 weeks before taper, his athletes can sustain 45–55 minutes at threshold pace — a remarkable stimulus that directly transfers to half marathon performance.

For pace calculator users, Pfitzinger recommends that your half marathon goal pace should be between your current threshold pace and your current marathon pace. If your threshold pace is 4:30/km and your marathon pace is 5:00/km, a realistic half marathon pace is 4:40–4:50/km.

Hansons Half Marathon Method: Running on Tired Legs

The Hansons method, originally developed for the marathon, has been adapted for the half marathon with equal effectiveness. The core philosophy remains cumulative fatigue — the idea that training adaptations are maximized when quality sessions are performed on legs that haven't fully recovered from previous efforts.

The Hansons half marathon schedule runs 6 days per week with a structure that accumulates 45–65 miles per week at peak:

• Tuesday – Speed work: 12 × 400m at 5K pace, or 6 × 800m at slightly slower than 5K pace. Develops running economy and VO2 max.
• Thursday – Tempo/Strength: 6–10 miles at half marathon goal pace to 15 seconds faster. The backbone of the program — teaches your body exactly what race day feels like.
• Sunday – Long run: 12–15 miles at easy to moderate effort. Shorter than traditional plans but performed on legs with 4–5 days of accumulated fatigue.
• Mon/Wed/Fri/Sat – Easy runs: 5–8 miles at easy effort. These maintain volume and promote recovery between quality days.

The Hansons philosophy argues that a 15-mile long run performed on legs already carrying 40 miles of accumulated weekly fatigue provides the same physiological stimulus as a 18–20 mile long run done on fully rested legs. The practical benefit: less injury risk, faster recovery, and more consistent week-to-week training without the boom-bust cycle of massive long runs followed by recovery weeks.

For pace calculator users targeting their first sub-2:00 half marathon, the Hansons approach would have you running tempo sessions at approximately 5:30–5:35/km (just under goal pace of 5:41/km) for 6–8 miles by peak training. If you can achieve this on a Thursday after running 5–6 miles on Monday, Tuesday, and Wednesday, you're ready to race.