What Heart Rate Zone Should You Run In? A Runner's Guide
"What heart rate zone should I run in?" is one of the most common questions new runners ask — and the honest answer is: it depends what the run is for. A recovery jog, an easy long run, and a hard interval session should all feel (and measure) completely different on your chest strap or watch. Running everything at the same effort is one of the most common reasons runners plateau or get hurt.
This guide walks through the five heart rate zones in plain language, which one you should be in for which kind of run, and how to work out your own numbers. If you want to skip the explanation and get your personal zones right now, our free heart rate zone calculator does the math for you using the Karvonen formula — you just need your age and resting heart rate.
The five heart rate zones, in plain English
Every major coaching system (Garmin, Polar, TrainingPeaks) uses some version of this five-zone model. The percentages differ slightly depending on the formula, but the physiology behind each zone is the same:
- Zone 1 — Recovery. Very easy, fully conversational. This is your warm-up, cool-down, and true recovery-day pace. If you're not sure whether you're in Zone 1, you probably are.
- Zone 2 — Aerobic (Easy). Comfortable, sustainable, still conversational but you notice your breathing. This is the effort your easy runs and most of your long runs should live in.
- Zone 3 — Tempo. Moderately hard — you could speak in short sentences, not paragraphs. Marathon race pace usually sits around here for recreational runners.
- Zone 4 — Threshold. Hard, but sustainable for 20–40 minutes if you had to. This is "comfortably uncomfortable" — the effort of a tempo run or threshold interval.
- Zone 5 — VO₂max / Max effort. All-out. Sustainable for a few minutes at most. Short, hard intervals live here.
Why most of your running should be in Zone 2
This surprises a lot of new runners: the majority of your weekly mileage — roughly 70–80% for most marathon and half-marathon training — should be in Zone 1–2, not somewhere in the "medium-hard" middle ground. Zone 2 training is where your body builds mitochondria, gets better at burning fat for fuel, and increases the amount of blood your heart pumps per beat — all without piling up the fatigue that comes from running hard every day.
The mistake most self-coached runners make is running their easy days too hard and their hard days not hard enough — everything ends up in a grey, medium-effort zone that's too taxing to recover from but not intense enough to drive real fitness gains. This is exactly the kind of pattern an AI running coach is built to catch, because it can see your actual heart rate data run after run, not just guess from how you say you felt.
Based on your profile, your Zone 2 ceiling is around 152 bpm — so 165-170 bpm on an "easy" run is actually Zone 3-4 territory for you. That's a common pattern, and it usually means your easy days aren't giving you the recovery they're supposed to.
| Zone | Your Range | What it should feel like |
|---|---|---|
| Zone 2 (target) | 128–152 bpm | Comfortable, fully conversational |
| Your recent easy runs | 165–170 bpm | Tempo effort, not recovery |
What to do:
- 🔴 Slow down 30–45 sec/km on your next 3 easy runs, even if it feels unnaturally slow at first
- ✅ Keep your hard sessions hard — the fix isn't running less intensely overall, just more deliberately by zone
I'll adjust your pace targets for this week's easy runs and watch how your resting HR trends over the next 7 days.
Real PacecraftAI response — actual output from the app
How to find your own heart rate zones
The simplest formula (220 minus your age) gives a rough estimate of max heart rate, but it ignores your resting heart rate — which varies a lot between individuals and says a lot about your fitness level. Two 35-year-olds with the same max heart rate but resting heart rates of 45 and 70 bpm should not be training in the same zones.
The more accurate approach is the Karvonen formula, which uses your Heart Rate Reserve (max HR minus resting HR) to calculate personalised zones:
- Heart Rate Reserve (HRR) = Max HR − Resting HR
- Target HR = (HRR × zone %) + Resting HR
Rather than doing this by hand, plug your age and resting heart rate into our free heart rate zone calculator and get all five zones instantly, in beats per minute.
PacecraftAI uses your real resting heart rate and HRV data — not just an age-based estimate — to set your training zones automatically, and adjusts them as your fitness changes. Try it free →
Which zone for which run?
- Recovery jog / cool-down: Zone 1
- Easy run, most of your long run: Zone 2
- Marathon race pace (for most recreational runners): Zone 3
- Tempo run, threshold intervals: Zone 4
- Short hard intervals (1–3 min): Zone 5
If you're following an AI-generated training plan, the specific zone for each session should already be built in based on your goal race and current fitness — but it's still worth understanding why each session is prescribed at the effort it is, so you know when to trust the plan and when something feels genuinely off.
The practical takeaway
You don't need a lab test or an expensive watch to start training by heart rate zone — just your age, your resting heart rate, and a chest strap or wrist-based monitor that's reasonably accurate. Get your numbers with our heart rate zone calculator, keep your easy days genuinely easy, and save the hard efforts for the sessions designed to be hard. That single change is one of the highest-leverage things a self-coached runner can do.