Most runners train at one pace: somewhere between easy and hard, every day. Jack Daniels' five-zone system is different. Enter any recent race result and this calculator returns precise per-kilometre targets for Easy (aerobic base), Marathon (race-specific endurance), Threshold (lactate ceiling), Interval (VO2max stimulation), and Repetition (speed economy). Five distinct training stimuli. One number in. Use the result in your next session.
Use a recent race, a park run, or a hard time trial. The more rested you were, the sharper the VDOT signal.
| Zone | Per km | % VO2max | Primary use |
|---|---|---|---|
| EEasy | — | 59–74% | Recovery runs, easy long runs, warm-up, cool-down |
| MMarathon | — | ~84% | Long runs with marathon-pace segments, progression runs |
| TThreshold | — | ~88% | Tempo runs 20–40 min, cruise intervals, threshold reps |
| IInterval | — | ~98% | VO2max reps 3–5 min, 800m–1200m track intervals |
| RRepetition | — | ~105% | Speed economy strides, 200m–400m fast reps, neuromuscular work |
Jack Daniels, exercise physiologist and Olympic coach, developed a training framework built around five discrete intensity zones, each tied to a specific percentage of an athlete's maximal oxygen uptake (VO2max). The system works because different percentages of VO2max produce different physiological adaptations. Training at a mix of all five zones, in roughly the right proportions, develops every component of running fitness simultaneously.
The zones are derived from VDOT — Daniels' shorthand for the VO2max implied by a race performance. VDOT strips out luck, weather, and pacing error and returns a single fitness number. From that number, all five training paces follow mathematically. Two runners with the same VDOT run the same training paces even if one is a 70 kg sub-elite and the other is a 90 kg recreational jogger. The number is the number.
The power of the system lies in what it prevents. Without precise pace targets, runners tend to do most of their volume in a grey zone: too hard to recover from, too easy to produce threshold adaptation. The five-zone framework forces a clean separation between easy days and hard days, between pace zones that build aerobic capacity and pace zones that sharpen speed. Vague training produces vague fitness. Precise paces produce measurable improvement.
Easy pace covers 59 to 74 percent of VO2max and represents the widest zone in the system. For most runners, that is a genuinely conversational effort: sentences come out unbroken, breathing is audible but not labored, and the perceived effort sits well below a seven on a ten-point scale. The zone is intentionally broad because easy running serves several different purposes depending on where it falls in the training week.
Recovery runs at the slow end of E pace (around 59–65% VO2max) accelerate lactate clearance, loosen muscles after a hard session, and add aerobic volume without accumulating meaningful fatigue. Long runs at the faster end of E pace (65–74% VO2max) build mitochondrial density and fat-burning capacity, teach the body to stay aerobically efficient at sustained duration, and are the single most important structural session in any marathon or half marathon program.
The most common mistake with easy pace is running it too fast. When an easy run creeps up toward marathon pace, it stops being aerobic base work and becomes a moderate-effort session — too hard for genuine recovery, too slow for threshold adaptation. If your heart rate pushes above your aerobic threshold zone during what should be an easy run, slow down. The pace on the watch matters less than the physiological zone you are actually training.
Daniels recommends that approximately 65–75% of total weekly volume sits in E pace, which makes it the single most important pace in the system by volume. Getting easy pace genuinely easy is the prerequisite for getting hard days genuinely hard.
Marathon pace (84% VO2max) is the most race-specific zone for runners targeting a marathon or half marathon. Running at M pace in training teaches the neuromuscular and metabolic system to sustain goal-race effort efficiently without the full cost of a race. Longer tempo runs and the pace segments embedded in long runs typically target M pace. It is hard enough to constitute genuine quality work, but slow enough that the recovery debt is manageable within a busy training week.
Threshold pace (88% VO2max) is where lactate clearance and production are in approximate balance — what coaches call the lactate threshold or anaerobic threshold. Running slightly above this pace tips the balance toward lactate accumulation and makes the effort unsustainable beyond roughly 40 to 60 minutes. Running right at it, in controlled doses, is the most direct training stimulus for raising the threshold pace itself. A higher threshold pace means you can sustain faster running before lactate builds — the core mechanism behind racing improvement in distances from 5K to marathon.
Classic threshold sessions include a 20 to 40 minute continuous tempo run at T pace, or cruise intervals of 3 to 5 repetitions of 6 to 8 minutes each with 1 minute recovery. Both formats are available in Get-Split's workout library, calibrated to your individual T pace derived from your VDOT. The key is honesty with the pace target — T pace is not "comfortably hard," it is a specific physiological zone, and running it 10 seconds per kilometre too fast turns a threshold session into an interval session with inadequate recovery.
Interval pace (approximately 98% VO2max) is the hardest sustained training effort in the Daniels system. Sessions at I pace target the highest end of aerobic capacity, stimulating the cardiovascular system to deliver oxygen at close to its ceiling rate. Individual reps typically run 3 to 5 minutes — long enough to fully load the aerobic system, short enough to maintain the target pace throughout. Classic formats are 1000-metre or 1200-metre track intervals with 3 to 4 minutes of easy jogging recovery.
The constraint on I-pace training is not fitness but recovery. Because the sessions approach maximal aerobic stress, they require 48 to 72 hours of easy training afterward before quality can be repeated. Most structured training plans include one I-pace session per week in the VO2max development phase, typically 3 to 6 repetitions totaling 5 to 8 kilometres of I-pace work in a session. More than that does not produce additional adaptation; it produces fatigue.
Repetition pace (approximately 105% VO2max) is faster than race pace at any distance. Short reps — 200 to 400 metres — run at R pace develop running economy: the mechanical efficiency with which the neuromuscular system converts metabolic energy into forward motion. Better economy means faster racing at the same aerobic cost. R-pace sessions are not cardiovascularly demanding in the way interval sessions are; the aerobic system barely reaches full output in 40-second efforts. The training stimulus is neuromuscular. Full rest between reps (the ratio is typically 1 minute rest per 200 metres of effort) is essential — partial recovery turns R-pace reps into underpaced interval work.
Knowing all five paces is different from knowing how to distribute them. Daniels' recommended weekly structure for most competitive runners follows a pattern: the majority of volume in E pace, one threshold session, one interval or repetition session, and a long run at E pace. The exact proportions depend on training phase and goal distance.
In a base-building phase (12 or more weeks from race day), the emphasis sits on E pace and M pace: high aerobic volume, one threshold session per week, minimal I or R work. In the sharpening phase (4 to 8 weeks out), I-pace intervals displace some of the threshold work, and R-pace strides appear after easy runs to maintain neuromuscular speed. In the final 2 to 3 weeks of taper, volume drops sharply but all five pace types remain present in reduced doses to keep the system primed.
The calculator above gives you the raw material. Get-Split's plan engine uses those same five paces to build a full structured program, pushing the interval and tempo workouts directly to your Garmin device so the pace targets appear on your watch during the session. The plan adapts as your VDOT changes — recalculate after every significant race and your entire training plan shifts accordingly.
Build a plan around my paces →A 5K or 10K run at full effort on a flat course gives the sharpest VDOT signal because those distances require close to maximal aerobic output throughout. A 10K is often considered the most reliable input — long enough that pacing error averages out, short enough to sustain near-VO2max intensity for the full duration. Marathons are valid inputs but require significant caution: pacing strategy, glycogen depletion, and temperature have larger effects on marathon time than on 5K or 10K time, so a slow marathon in heat may understate your actual fitness. If in doubt, use a 5K or 10K from the last 6 weeks.
Recalculate after every significant race or time trial, and at minimum every 8 to 12 weeks during a structured training block. Aerobic fitness improves steadily over a training cycle, and paces set from a fitness test 16 weeks ago are likely too conservative by the end of the block. Running at outdated E pace is fine — it is still aerobic work — but running interval and threshold sessions from a stale VDOT means you are training below your current capability and missing the adaptation stimulus. A fresh 5K time trial every 2 to 3 months is sufficient for most recreational runners.
Almost certainly not. Easy pace for most runners is genuinely slow — often 60 to 90 seconds per kilometre slower than threshold pace. The calculator is mathematically correct at 59–74% VO2max. If your E pace feels embarrassingly slow, that is usually a sign that your easy runs have been chronically too fast rather than a sign that the zone is wrong. Runners who commit to genuine E pace for 8 to 12 weeks typically find their E pace speed increases substantially at the same heart rate — not because the zones shifted, but because their aerobic base improved. The initial slowness is accurate feedback, not an error.
Marathon pace sits at approximately 84% of VO2max, threshold pace at approximately 88%. The gap between them is typically 10 to 20 seconds per kilometre depending on the runner. Marathon pace is the fastest effort you can sustain for the full 42.2 kilometres; threshold pace is the fastest you can sustain for roughly 40 to 60 minutes. Both train the lactate system, but threshold pace produces a stronger direct stimulus for raising the lactate threshold itself, while marathon pace is more race-specific for marathon training and produces less fatigue per session. Well-structured plans include both in the same training block, not one or the other.
Yes, with two caveats. First, the time trial must be a genuine maximum effort — not a comfortable fast run. Daniels' formula assumes you raced to your limit. A time trial where you held back by even 5% will underestimate your VDOT and produce training paces that are too slow. Second, solo time trials tend to produce times 1 to 3 percent slower than equivalent race efforts, because competitive environment and pacing by other runners provide a genuine performance boost. Adjust your time trial result downward by 1 to 2% before entering it here, or accept that your VDOT may be slightly understated and your training paces slightly conservative.
The two systems describe the same physiological zones with different metrics. Easy pace corresponds to Zone 1 to Zone 2 in a five-zone heart rate model (below approximately 85–89% of lactate-threshold heart rate). Threshold pace corresponds to Zone 4 (95–99% LTHR). Interval pace sits at or above Zone 5 (above 100% LTHR). Pace zones are objective and weather-independent; heart rate zones account for variables like heat, fatigue, and altitude that pace cannot capture. Use pace zones as primary targets for threshold and interval sessions on controlled flat courses. Use heart rate as the ceiling on easy runs when conditions make pace unreliable. The heart rate zone calculator gives you the complementary HR targets for each training zone.