Calculate your training zones for free

Heart rate zones: how they work

What each HR zone (Z1 to Z5) is and what it's for

Heart rate zones split your effort range into 5 bands, from easiest (Z1) to hardest (Z5). Each one trains something different: Z1 and Z2 build the aerobic base everything else depends on —if you want to understand why most of your volume should live there, this zone 2 running guide breaks it down in detail. Z3 is the zone most runners abuse without noticing —training's "gray zone," neither truly easy nor truly hard— while Z4 and Z5 reserve real effort for intervals and race pace. Training without knowing your zone is like planning a route with no map: you're moving, just not necessarily where you meant to go.

How it's calculated: % max HR vs. the Karvonen formula

The simplest method uses a straight percentage of your max heart rate (50-60% for Z1, up to 90-100% for Z5). It's quick, but it ignores something important: your resting heart rate, which varies a lot between athletes with the same max HR. The Karvonen formula (1957) fixes this by calculating your "heart rate reserve" —the gap between your max and resting HR— and applying the percentage to that reserve instead of the max. Two runners with a max HR of 185 can end up with quite different zones if one has a resting HR of 45 and the other 70. That's why this calculator asks for resting HR as an optional field: if you have it, Karvonen gives you a result tuned closer to you specifically.

Common mistakes when calculating your HR zones

The most common one: using "220 minus age" blindly. It's a population average with a margin of error of ±10-12 beats —enough to land you in the wrong zone without knowing it. If you have a real max HR reading (from a test or an all-out race effort), use that instead of the age formula. The second mistake is skipping resting HR when you actually have it: it's a free data point that sharpens the Karvonen calculation. The third is trusting a wrist-based sensor during hard efforts, where it's less reliable than a chest strap —if your Z4/Z5 zones don't match how the effort actually feels, suspect the sensor first. To see where you're really landing, this heart rate vs. power comparison compares heart rate and power side by side, workout by workout.

Training paces (VDOT): from your race time to your daily paces

What VDOT is and where it comes from

VDOT is a number —not a real physiological unit, but an index— that American coach and exercise physiologist Jack Daniels developed together with Jimmy Gilbert to summarize your current aerobic fitness from a single race result. The higher your VDOT, the faster your paces at any distance. Its real value is that, from that one number, the 5 training paces (E, M, T, I, R) documented by Daniels in Daniels' Running Formula fall out automatically, so you don't have to calculate each one by hand or guess by feel. It's the most widely used reference system in structured running, used by coaches and everyday runners alike.

How your E / M / T / I / R paces are calculated from a recent race

You enter a distance (5K, 10K, half, or marathon) and your time; the calculator translates that result into your VDOT and, from there, into your 5 daily paces. E (easy) is where most of your weekly mileage lives; M (marathon pace) is what you'd hold for 42 km today; T (threshold) is fast but sustainable, roughly your one-hour race pace; I (intervals) raises your aerobic ceiling with 3K-5K-effort work; and R (repetition) is pure speed, faster than race pace, with long recoveries. If you're building toward a specific goal —a marathon, a 70.3— these paces are the real starting point for planning your weeks, not just "running fast" with no structure: this Ironman 70.3 Vitoria 2026 build-up shows how they apply to a real endurance goal.

Common mistakes when calculating training paces

The costliest mistake: using an old race result. Your VDOT changes with your fitness, so a 10K from 8 months ago can give you paces that are too conservative (if you've improved) or too optimistic (if you've lost fitness). Always use your most recent time and, if possible, from an actual race —training-only time trials tend to run slower than your true fitness. The second mistake is blending race pace with training pace: running your easy runs at threshold pace "because you feel good" piles up fatigue you won't notice until it catches up with you. The third is ignoring terrain or weather on the day of the race: a windy or hilly 10K isn't worth the same as a flat one. If your current plan isn't producing results despite training hard, this guide on why your training plan isn't working walks through the most common causes.

Power zones (FTP): the Coggan model

What FTP is and why it's cycling's reference metric

FTP (Functional Threshold Power) is the maximum power you can sustain for roughly one hour without falling apart. It was popularized by Andrew Coggan and Hunter Allen in Training and Racing with a Power Meter, and it became cycling's reference metric with a power meter for a simple reason: unlike heart rate, power doesn't shift with heat, caffeine, or a stressful day —watts are watts. Knowing your FTP lets you plan every session as a percentage of your real capacity, instead of riding "by feel." If you're still gauging effort by feel, this guide on how to calculate your cycling FTP goes into detail on how to get it, with or without a formal test.

How the 6 power zones are calculated from your FTP

Once you have your FTP, the Coggan model splits it into 6 zones, each with its own training purpose: Z1 (active recovery) for the day after a big effort; Z2 (endurance) where you build your aerobic base on the bike; Z3 (tempo), a firm, sustained effort; Z4 (threshold), the zone where your FTP lives and where you train the ability to hold near-max effort; Z5 (VO2max) for hard, few-minute intervals; and Z6 (anaerobic capacity) for very short, very intense efforts with long recovery. Entering your FTP into the calculator gives you the exact wattage for each zone, ready to set up on your bike computer or training app. If you also want to understand how that effort accumulates week over week, this TSS, CTL and ATL guide explains TSS and training load built on these same zones.

Common mistakes when calculating your FTP

The most frequent one: a poorly executed 20-minute test —without a proper warm-up, or starting too hard and fading at the end— which gives you an artificially low FTP. The second is not retesting: your FTP shifts with your fitness, so a value from 4 months ago no longer reflects your current level; retest every 6-8 weeks if you train regularly. The third is confusing FTP with your max sprint power —they're completely different things: a sprint lasts seconds, FTP holds for an hour. If you just calculated your FTP from a test, check this guide on how to calculate your cycling FTP to make sure you followed the right protocol before trusting the number.