The Complete Guide to Running Heart Rate Zones.

Heart rate training takes the guesswork out of pacing. Instead of wondering “is this too hard?” you look at your watch and the answer is on it. The catch: a heart rate zone system is only as accurate as the maximum heart rate it’s built on, and the formulas most people use are wrong by more than they realize.

This guide walks through how to find your real max HR, why the Karvonen formula is more accurate than percent-of-max for most runners, what each zone is for, and how to fit zones into a training week.

Definitions

• Maximum heart rate (HRmax): the highest beats-per-minute your heart can sustain under maximal effort. Genetic, declines slowly with age, and isn’t improved by training.
• Resting heart rate (RHR): beats-per-minute at full rest, ideally measured first thing in the morning before getting out of bed. Drops with aerobic training.
• Heart rate reserve (HRR): HRmax minus RHR. The “usable range” your heart operates in. Used by the Karvonen formula.
• Lactate threshold heart rate (LTHR): the HR at which blood lactate begins to accumulate; corresponds roughly to the pace you can hold for 60 minutes all-out.
• Karvonen formula: Target HR = (HRR × intensity%) + RHR (Karvonen, 1957). More accurate than percent-of-max because it accounts for individual fitness.
• Tanaka formula: HRmax = 208 - (0.7 × age) (Tanaka, 2001). More accurate than the older 220-age formula.

Finding your maximum heart rate

The famous “220 minus your age” formula is a textbook starting point and a poor real-world tool. Studies show its 95% confidence interval is roughly ±20 bpm — meaningless for prescribing training. The Tanaka formula (208 - 0.7 × age) is meaningfully better but still has standard error of around 7 bpm (Tanaka, 2001).

For accurate zones, do a field test. Two work well:

• Hill repeat test. Warm up for 15-20 minutes. Find a hill that takes 2-3 minutes to run hard. Run it three times, with 3-minute jog recoveries. Each repeat should feel harder than the last. The peak HR you see at the top of the third repeat is within 2-3 bpm of your true max.
• 5K race. A maximal 5K pulls roughly 95-100% of HRmax in the last kilometer. Add 1-2 bpm to your peak race HR.

Plug your tested or estimated max HR into our HR zones calculator to get your personalized zones.

Why resting heart rate matters: Karvonen vs percent-of-max

Two runners can have the same max HR (say, 190 bpm) but very different fitness. Runner A is detrained with a resting HR of 70. Runner B is well-trained with a resting HR of 50. Their hearts have different “usable ranges” — Runner A has 120 bpm of reserve; Runner B has 140.

The Karvonen formula (Karvonen, 1957) accounts for this. Instead of taking 70% of max, it takes 70% of the reserve and adds resting HR back in. For Runner A: (0.70 × 120) + 70 = 154 bpm. For Runner B: (0.70 × 140) + 50 = 148 bpm. The percent-of-max formula would give both the same target (133 bpm), which is too low for both.

If you know your resting HR (measure for 5 mornings, take the average), enter it into our calculator for Karvonen-based zones. If not, percent-of-max is a reasonable starting point.

The five zones

Zone 1: Easy / Recovery (50-70% HRR, ~65-79% HRmax)

Conversational pace. Full sentences. This is the zone where your aerobic base is built — capillary density increases, mitochondrial volume grows, fat oxidation improves. Most weekly running for any distance from 5K to ultra should be here. Recreational runners almost universally run this zone too hard. If you’re not slightly bored, you’re going too fast.

Zone 2: Aerobic / Marathon (70-80% HRR, ~80-87% HRmax)

Steady, controlled effort. You can speak in short phrases but not hold a flowing conversation. This is roughly marathon pace for trained runners. Long marathon-specific tempo runs and the second half of a long run live here.

Zone 3: Threshold / Tempo (80-90% HRR, ~87-92% HRmax)

“Comfortably hard.” You can manage 2-3 word answers. Lactate threshold sits at the upper edge of this zone. Threshold workouts (20-40 minutes of continuous tempo, or interval tempos like 4 × 8 minutes) train your body to clear lactate faster.

Zone 4: VO2max (90-95% HRR, ~92-96% HRmax)

Hard. Sustained for 3-8 minute intervals. This zone trains maximum oxygen uptake. Workouts: 5 × 1000 m at 5K pace, 6 × 800 m, or Yasso 800s. Most running plans include one VO2 session per week during build phases.

Zone 5: Anaerobic / Repetition (95-100% HRR, ~96-100% HRmax)

Maximum effort. 30 seconds to 2 minutes max. Trains neuromuscular speed, running economy, and lactate tolerance. Workouts: 200 m and 400 m repeats with full recovery, or hill sprints. Less is more — these workouts are not “more is better.”

The 80/20 rule (polarized training)

Stephen Seiler’s research on elite endurance athletes found a strikingly consistent pattern: roughly 80% of training time is spent at low intensity (Zone 1-2), and only 20% at moderate-to-high intensity (Zone 3-5). The “moderate intensity trap” — running too many sessions at threshold — produces fatigue without proportional adaptation.

For a recreational runner running 5 hours per week, that’s about 4 hours of easy running and 1 hour of harder work. Most recreational runners invert this: they run their hard sessions too easy and their easy sessions too hard, ending up with everything in the gray zone of moderate effort.

Practical application: a sample week

• Monday: rest or 30-minute Zone 1 walk/jog.
• Tuesday: intervals — 5 × 1000 m in Zone 4, with 90-second jog recovery in Zone 1.
• Wednesday: 45 minutes Zone 1.
• Thursday: tempo — 6 km at the bottom of Zone 3, sandwiched by easy warm-up and cool-down.
• Friday: 30-40 minutes Zone 1 or rest.
• Saturday: long run, all Zone 1, optional last 15 minutes drifting into Zone 2.
• Sunday: 30 minutes Zone 1.

Time-in-zone, not perceived effort, is the test. If your Zone 1 days creep into Zone 2-3 because you’re “feeling good,” your workout days will suffer.

Using HR with pace

HR and pace are complementary, not competing, metrics. Pace tells you how fast you’re going; HR tells you how hard your body is working. On any given day, the same pace can produce different HR depending on heat, hydration, sleep, and stress. The simplest workflow:

• Easy days: govern by HR. Stay in Zone 1, even if it means running slower than usual.
• Threshold and VO2 sessions: govern by pace (from training paces calculator). HR is a secondary check.
• Long runs: govern by HR for the first two-thirds, then by pace if doing marathon-pace work.

Common HR training mistakes

• Trusting “220-age.” The most overused and least accurate HR formula. Use Tanaka or test.
• Ignoring HR drift on long runs. HR drift (creep) of 5-10 bpm over 60+ minutes at constant pace is normal and reflects cardiovascular cost rising as heat and dehydration accumulate.
• Chasing HR in cold weather. Cold air suppresses HR; on a 0 °C morning, Zone 1 effort might pull 5-8 bpm lower than usual. Don’t push pace to “make HR right.”
• Comparing HR with friends. HR is genetic. A 195 max isn’t fitter than a 175 max; it’s just different physiology.
• Using wrist-based HR for intervals. Optical sensors lag and can lock onto cadence. For accurate interval HR, a chest strap is meaningfully better.

What this means for your training

Two changes pay back the most. First, slow your easy days down — every easy run, every recovery jog. The boredom is the workout. Second, do hard sessions hard. If your tempo run is supposed to be Zone 3 and you’re sitting in Zone 2, you’re banking fatigue without earning fitness.

Get your zones from the HR zone calculator, line them up against your pace zones from the training paces calculator, and start governing easy days with HR.

FAQ

What is “Zone 2 training” and why is it popular? Zone 2 in the popular discourse usually means roughly 70-80% of max HR — solid easy aerobic running. Its popularity comes from research showing that high volumes of low-intensity training drive fat oxidation, mitochondrial density, and aerobic capacity in ways that high-intensity sessions don’t replace.

What’s a normal max heart rate for a 40-year-old? Tanaka predicts roughly 180 bpm for a 40-year-old, with a standard error of about 7 bpm. Real values commonly range from 165 to 195 bpm. Test instead of guess.

Should I train by HR or by pace? Both, in different contexts. HR is best for easy and long efforts; pace is best for tempo and intervals. The two together give you a much fuller picture than either alone.

My HR runs high in summer. Am I unfit? Heat stress raises HR at any given pace by 5-15 bpm. If you’ve been training in cooler weather, expect a temporary spike when summer arrives, then a re-equilibration over 10-14 days as you heat-acclimatize.

Do I need a chest strap? For tempo and easy runs, wrist-based optical HR is fine. For intervals — where HR changes fast and you need accuracy in the first 60 seconds — a chest strap or upper-arm sensor is meaningfully more accurate.

Why is my morning HR higher some weeks? Elevated morning HR (5+ bpm above your baseline) is one of the better signals of incomplete recovery, illness, or psychological stress. If it’s high for 3+ days, take a recovery day.