Half Marathon Calculator

Half Marathon Calculator — calculate half marathon for training and performance. Evidence-based formula and benchmarks.

A running pace calculator converts between pace (time per mile or kilometre), speed (miles per hour or km/h), and finish time for any distance — from 5K to ultramarathon. Whether you are targeting a Boston Qualifier, planning a training run at an easy effort, or calculating splits for a goal race, knowing your required pace is fundamental to smart training and racing.

Running pace calculators are used by beginners setting their first race goals, competitive runners dialling in race strategy, and coaches building training plans with specific effort zones. Compare the training zone calculator for effort targets and the cycling power calculator for another endurance-sport performance measure.

Choose what you want to calculate: finish time from pace and distance, pace from finish time, or distance from pace and time.
Enter the known values — e.g. goal finish time of 3:30:00 for a marathon.
The calculator returns your required pace per mile and per kilometre.
Use the splits table to plan how each mile should feel — negative splits (running the second half faster) are most effective for marathon racing.
Cross-reference your target pace against your recent training runs to confirm it is realistic.

Pace and speed formulas

Pace (min/mile) = total time (minutes) / distance (miles)

Speed (mph) = distance (miles) / total time (hours) = 60 / pace (min/mile)

Finish time = pace (min/mile) × distance (miles)

Common race distances: 5K = 3.107 mi, 10K = 6.214 mi, Half marathon = 13.109 mi, Marathon = 26.219 mi

Understanding your pace results

Pace zones and effort levels

Easy/recovery runs: 60–75 seconds per mile slower than marathon pace. Long run pace: 45–90 seconds per mile slower than marathon pace. Tempo/threshold pace: approximately 25–30 seconds per mile slower than 10K race pace. If your target marathon pace is 8:00/mile, your easy runs should be around 9:00–9:30/mile. Running too fast on easy days is the most common training mistake — it increases injury risk without proportional fitness gains.

Sports tips and best practices

Use a recent race result to predict your goal pace — a 10K time × 4.65 gives an approximate marathon finish time.
Start your long runs and races slower than goal pace — it is far easier to speed up at the end than to recover from going out too fast.
Account for elevation: add approximately 20–30 seconds per mile for every 1% average gradient on hilly courses.
Heat slows pace: add 20–30 seconds per mile when running in temperatures above 60°F (15°C) compared to ideal conditions (50–55°F).

The Boston Marathon qualifying standards (2024) range from 3:00:00 (men 18–34) to 5:25:00 (women 80+) — entry requires running 5 minutes under your age-group standard.
The world marathon record is 2:00:35 (Kelvin Kiptum, 2023) — a pace of 4:35/mile (2:51/km) for 26.2 miles.
The average US marathon finish time is approximately 4:29 for men and 4:57 for women (Running USA, 2023).

Common mistakes to avoid

Setting a goal pace based on a "good day" PR without accounting for current fitness — be honest about your recent training.
Running every training mile at the same effort — polarised training (mostly easy, some hard) produces better adaptations than running everything at moderate effort.
Ignoring mile splits during a race — watching average pace on a GPS watch hides whether you are surging and recovering dangerously.

Pace predictions are estimates based on mathematical models. Individual performance depends on training, health, weather, terrain, and race-day conditions. Consult a running coach for personalised race strategy, and a physician before beginning a running programme if you have health concerns.