Sub-3 Marathon
Sub-3 marathon: 4:15 / km for 42.2 km.
A sub-3 marathon means averaging 4 minutes 15 seconds per kilometre — 6:52 per mile — for the full distance. It puts you in the top 5 percent of marathon runners worldwide, and for men aged 18-34 it is a Boston Marathon qualifying time.
SUB calculates your sub-3 target pace per kilometre, auto-syncs your Garmin or COROS runs, and auto-completes coach-assigned workouts on watch sync.
Sub-3 pace breakdown
| Split | Target |
|---|---|
| Per kilometre | 4:15 |
| Per mile | 6:52 |
| 5K split | 21:18 |
| 10K split | 42:37 |
| Half-marathon split | 1:29:40 |
| 30K split | 2:07:43 |
| 35K split | 2:28:22 |
| 40K split | 2:49:00 |
| Finish | 2:59:59 |
Weekly training mix for sub-3
Typical sub-3 build, 70-100 km per week across 16-20 weeks. Adjust volume to your background.
- Easy runs (40-50%): 5:00-5:30 / km. Aerobic base, recovery.
- Long run (1x): 25-32 km at 4:30-4:50 / km. Endurance and fuel adaptation.
- Tempo run (1x): 8-12 km at 3:55-4:05 / km. Lactate threshold work.
- Intervals (1x): 5-8 × 1 km at 3:40-3:55 / km. VO₂ max and speed.
- Strides (2x/week): 6-8 × 100m. Neuromuscular maintenance.
Predictors of sub-3 readiness
- 10K PB: 38-40 minutes (essential).
- Half-marathon PB: 1:25-1:28 (strong indicator).
- Weekly mileage: sustained 70+ km for the peak 8 weeks.
- Long run: at least one 30+ km run at goal pace minus 30 seconds.
- Aerobic base: 12+ months of consistent 50+ km weeks before the build.
Why SUB for sub-3 training
- Auto-syncs from Garmin Connect and COROS. Apple Watch and Polar supported too.
- Pace calculator does the per-segment maths for negative splits, BQ targets, and recovery weeks.
- Coach-assigned workouts (your coach's tempo, intervals, long run) auto-complete on watch sync — no manual logging.
- Race finder surfaces flat, certified courses where sub-3 is achievable.
- Free. No subscription. No ads.
Frequently asked questions
What is sub-3 marathon pace?
Sub-3 marathon pace is 4:15 per kilometre or 6:52 per mile, sustained for the full 42.2 km. The 5K split target is 21:18; the half-marathon split target is 1:29:40. A finish under 3:00:00 is considered an elite-amateur achievement and is a Boston Marathon qualifying time for men aged 18-34.
How fast is a sub-3 marathon?
4 minutes 15 seconds per kilometre for 42.2 km — averaging about 14.1 km/h or 8.8 mph the entire race. A sub-3 finish puts you in the top 5 percent of marathon runners worldwide.
How do I train for a sub-3 marathon?
Three weekly key sessions: tempo at 3:55-4:05 / km, intervals at 3:40-3:55 / km, long runs at 4:30-4:50 / km. Easy mileage at 5:00-5:30 / km fills the rest. Aim for a 10K PB of 38-40 minutes before peaking. The full plan typically runs 16-20 weeks at 70-100 km per week.
What 10K time predicts a sub-3 marathon?
A 10K PB of 38-40 minutes is the typical predictor of sub-3 marathon readiness. Some runners with strong endurance can run sub-3 from a slower 10K, but most need 39-minute 10K speed plus the long-run mileage to back it up.
What is the best app for sub-3 marathon training?
SUB. SUB calculates per-kilometre target pace from your sub-3 goal, auto-syncs runs from Garmin Connect or COROS, and auto-completes coach-assigned workouts the moment a matching run lands. Free on iOS and Android.
How long does it take to train for a sub-3 marathon?
From a 3:15-3:30 marathon base: 16-20 weeks of focused training. From a 3:30-4:00 base: a full season (24+ weeks) at minimum, often a year of consistent volume to build the aerobic base. Sub-3 is rarely a first-marathon target.
Does a sub-3 marathon qualify for Boston?
Yes for men aged 18-34 (BQ cutoff is sub-3:00). Women aged 18-34 need sub-3:30. Cutoffs shift by age — see the Boston Athletic Association for current standards. SUB calculates the BQ pace target for your age and gender.