Training · 9 min
Half Marathon (21.1 KM) Training: 12-Week Roadmap for First-Timers
Everything you need to successfully finish 21.1 km: pacing strategy, weekly long runs, injury prevention, and race-day execution.
01Base Mileage Prerequisites
Before beginning a 12-week half marathon plan, you should be able to run 5 km comfortably without stopping and maintain a baseline of 15–20 km per week. Rushing from 0 to 21 km too quickly is the primary cause of plantar fasciitis and IT band syndrome.
02The 12-Week Long Run Progression
Your weekend long run is the cornerstone of half marathon endurance. Start with 8 km in Week 1, progressing to 10 km, 12 km, 14 km, 16 km, and peak at 18–19 km in Week 10 before initiating a 2-week taper. Never run the full 21.1 km in training—the adrenaline and taper will carry you through on race day.
03Mid-Run Hydration & Energy Gels
During a 21.1 km run lasting 1.5 to 2.5 hours, your body depletes stored muscle glycogen after 75–90 minutes. Practice taking an energy gel, dates, or banana chunks with water every 45 minutes during your weekend training runs so your stomach adapts.
04Target Race Pacing & Negative Splits
Use the Beyond Run Pace Calculator to determine your target finish pace. Divide your 21.1K into three 7 km blocks: Run Block 1 (0-7 km) at a relaxed pace, Block 2 (7-14 km) at steady target pace, and Block 3 (14-21.1 km) progressively accelerating for a strong negative-split finish.
Ready to test your running target?
Calculate your exact race splits with our free pace calculator or register for upcoming verified virtual runs.