Pace, time, and distance — the runner's triangle
In running, any two of these three determine the third. Given a pace and a distance, you can compute a finish time. Given a finish time and a distance, you can compute the required pace. This calculator works both directions, for the four classic race distances (5K, 10K, half marathon, marathon) plus any custom distance.
Reference paces by experience level
Beginner runners (new to running consistently)
- 5K: 32–40 min → 10:20–13:00 / mile
- 10K: 68–80 min → 10:50–13:00 / mile
- Half: 2:30–3:00 → 11:30–13:45 / mile
Intermediate (been running 6–18 months)
- 5K: 24–30 min → 7:45–9:45 / mile
- 10K: 50–65 min → 8:00–10:30 / mile
- Half: 1:50–2:15 → 8:25–10:20 / mile
- Marathon: 4:00–4:45 → 9:10–10:50 / mile
Experienced (2+ years, structured training)
- 5K: 20–24 min → 6:30–7:45 / mile
- 10K: 42–50 min → 6:45–8:00 / mile
- Half: 1:30–1:50 → 6:50–8:25 / mile
- Marathon: 3:15–4:00 → 7:25–9:10 / mile
The race-pace math
Your 5K time predicts your longer race times reasonably well. Classic rule of thumb: your 10K is roughly 2× your 5K + 1 min; your half is ~2.1× your 10K; your marathon is ~2.1× your half. These rules overstate performance for inexperienced runners and fade for very elite runners, but they're a useful sanity check when setting goals.
Even splits vs. negative splits
The simplest race plan is to run even splits — the exact same pace every mile. For 5K and 10K, this is often optimal. For longer races, negative splits (running the second half slightly faster than the first) produce better finish times and lower risk of blowing up. A 2% positive split (slowing 2% in the second half) is typical for struggling marathoners.
Why real races are slower than pace math predicts
- Course changes elevation. Hills cost more than they give back.
- Heat and humidity add 2–5% to finish times.
- Aid stations, traffic, weaving all add distance and time.
- Fatigue drift is non-linear — final miles are almost always slower than opening miles.
Finding your goal pace
A recent race or time trial is the most reliable input. If you haven't raced, do a 4-mile time trial on flat terrain — your 5K pace will be roughly 15 seconds/mile faster than that test. Alternatively, use your training-run pace at a 4/10 perceived effort and subtract 45–60 sec/mile for your 5K race goal.
Pace training zones
- Easy: 60–75 sec/mile slower than your 5K pace. Used for 70–80% of weekly miles.
- Marathon pace: 45–60 sec/mile slower than 5K pace.
- Half-marathon pace: 15–30 sec/mile slower than 5K pace.
- Tempo: your 10K pace, sustainable for 20–40 minutes.
- VO2 max intervals: 3K–5K pace, held for 3–5 minutes at a time.
The heart rate zones calculatoris the heart-rate companion to these pace zones. They don't perfectly correspond, but the mapping is close for trained runners.
Fueling and hydration
Under 60 min: water only. 60–90 min: consider a gel midway. 90+ min: 30–60 g carbs per hour, alternating with water. Marathon: 60–90 g carbs per hour for experienced runners. The water intake calculator and walking calories calculator are complementary tools for planning longer outings.
Training volume by race distance
- 5K: 15–30 miles/week peak.
- 10K: 20–40 miles/week peak.
- Half marathon: 25–50 miles/week peak.
- Marathon: 35–70 miles/week peak.
Don't increase weekly mileage by more than ~10% per week. Peak training volume should be reached 2–3 weeks before the race, followed by a taper.
FAQ
Does the calculator account for hills?
No — it assumes constant-pace, flat running. For hilly courses, add 1–3% to expected finish time depending on elevation gain.
Should I wear a pace chart on race day?
A paceband — simple splits printed on your arm — is more useful than a GPS watch for most people. GPS paces are noisy (sometimes 10-15 sec off), and chasing the watch usually produces erratic splits.
What's a "good" 5K time?
Sub-30 is a common general fitness benchmark. Sub-25 is solid. Sub-20 is competitive for age-group runners. Elite is sub-14 (men) or sub-16 (women).
How do I convert pace between units?
Mile pace × 0.621 = km pace. Or use the calculator's switch to toggle; it recomputes automatically.