Free marathon pace timer for tracking race segments and target splits. Set target pace per km or mile and time each segment of your long run. Start instantly.
Divide your target finish time by 42.2 (km) or 26.2 (miles). For a 4-hour marathon: 240 minutes ÷ 42.2km = 5:41/km (9:09/mile). For sub-3 hours: 180 ÷ 42.2 = 4:16/km (6:52/mile). Add 10–15 seconds/km to the first half (negative split strategy) for optimal race execution.
Running the second half faster than the first. World marathon records are set with near-even or negative splits. Running the first half too fast causes glycogen depletion and a significant slowdown after 30km (the "wall"). A 10–20 second/km conservative first half improves final time despite seeming counterintuitive.
The long run peaks at 30–35km (18–22 miles) approximately 3–4 weeks before race day. Run at 60–90 seconds per km slower than marathon pace. The long run builds aerobic base, fat utilisation, and mental endurance. Do not exceed 3 hours of running — beyond this, recovery cost outweighs training benefit.
Easy runs (80% of training): 60–90 seconds per km slower than marathon pace. Tempo runs (15% of training): marathon pace to 30 seconds faster. Intervals (5% of training): 5k pace. Running too fast on easy days is the most common marathon training mistake — it impairs recovery and reduces quality of hard sessions.
The "wall" at 30–32km marks glycogen depletion in most undertrained or under-fuelled runners. Pace can drop 30–60 seconds per km. Proper carbohydrate loading (3 days before), consistent fuelling from 5km intervals during the race, and conservative early pacing prevent or delay hitting the wall.