Goal time to per-km and per-mile pace with even-split checkpoints every 5 km, halfway split, and speed in km/h and mph — the race plan on one board.
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FORMULA USEDMarathon Pace Calculator
From goal time to goal pace
A marathon goal only becomes a plan once it is divided across the distance: goal seconds ÷ 42.195 km = seconds per kilometer (the marathon is 26.2 miles because it is 42.195 km — the 1908 London Olympic distance, plus those famous 385 yards in the stadium). A 3:30:00 goal is 12,600 seconds, or 4:59 per kilometer and 8:01 per mile.
Reading the 5K checkpoints
The table marks your watch at every 5 km so a race never drifts unnoticed: 24:53 at 5 km, 1:45:00 at halfway, 3:19:05 at 40 km for a 3:30 goal. Checkpoints every 5 km suit races with kilometer markers; if your watch is set to miles, the per-mile pace row is the number to hold on average.
Choosing a goal worth pacing
Pick the goal from recent races, not from ambition. A half-marathon finished in 1:45 points at roughly a 3:40–3:45 marathon with proper training; the pace implied by 1:38 or better maps near 3:30. If the checkpoint times from your goal look 10+ seconds per km faster than your current half pace converts to, the goal is a next-season goal.
12,600 ÷ 42.195 km = 298.6 s/km = 4:59 /km, or 8:01 /mile.
Checkpoints: 5 km at 24:53, halfway at 1:45:00, 40 km at 3:19:05.
Cross the line at 3:30:00 — 21 seconds of cushion keeps it "sub".
How to use it
Choose marathon or half marathon distance.
Enter your goal finish time as hours, minutes, seconds.
Read the pace in both units plus your halfway split.
Carry the 5 km checkpoint table to the course — compare watch to plan at each mark.
Frequently asked questions
How do I calculate my marathon pace?
Convert the goal time to seconds and divide by 42.195 km (or 26.2 mi). A 3:30 goal is 12,600 seconds, which is about 4:59 per kilometer or 8:01 per mile. The calculator also lays out the elapsed time at every 5 km checkpoint so you can check progress mid-race.
What is a good marathon pace for beginners?
First-time marathoners commonly finish between 4:30 and 6:00, roughly 6:20–8:30 per kilometer. A finish-first goal of about a minute per kilometer slower than your 10K race pace is a sensible place to start, with the option to negative-split the final 10 km if the day goes well.
Should I train faster than my goal pace?
Some of the week, yes: one interval or tempo session above goal pace builds speed and makes goal pace feel sustainable. But most kilometers should be genuinely easy, and the long run should practice goal pace only in segments — training always at goal pace is a classic route to the wall.
Does this tool account for hills or weather?
No — the checkpoints assume dead-even pacing on a flat, certified course at neutral temperature. Add 5–10 seconds per kilometer for significant hills, and expect heat above about 60°F (15°C) to slow the second half noticeably; adjust the goal before the gun, not during.
Can I use a half marathon time to guess marathon pace?
As a rough anchor, yes: doubling your half time and adding 10–15 minutes approximates a well-trained marathon. A 1:45 half points at about 3:40–3:45. If you have never run over 30 km in training, respect the wider end of that adjustment.
How accurate is the finish time from a given pace?
Arithmetically exact, physically approximate. The multiplication assumes you can hold the pace for 42.195 km, and fatigue makes that harder with every kilometer — which is why the goal should come from race results and training long runs, with this table translating the goal into splits.