Heart rate zones are a way to describe how hard you're working during a cardio workout, like running or cycling. The faster your heart beats, the harder you're working. So an easy jog might have you in zone 2 for a whole workout, while a HIIT workout might have you bouncing between zones 1 and 5. Read on for a breakdown of what heart rate zones are, how to use them, and some of the caveats you should know when you're training this way. One quick thing before we dive in: heart rate zones are for cardio. Cardio means exercise that involves doing the same rhythmic movement over and over, like running or swimming or stair climbing. Heart rate zones mean nothing for strength training, even if you have an app or watch that reports them to you as if they matter. Don't worry too much about zones as a beginnerI'm going to start with a huge caveat. You may hear everybody talking about zone this and zone that, but if you're new to exercise or new to heart rate tracking, you're actually better off ignoring zones for a while. Pay more attention to how you feel. A workout that's meant to be easy should feel easy, regardless of what number is on your heart rate monitor. A workout that's meant to be hard should feel hard. Over time, if you watch your heart rate during exercise, you'll start to notice which numbers go with which feelings. Knowing that you see (for example) 140 on your watch when you're in the middle of an easy workout means a lot more than knowing that your device considers it to be "zone 2." Zone workouts are hard for beginners to follow, for a few reasons: Your zones may be hard to stay in, especially the lower zones like zone 2. If your heart rate skyrockets into zone 4 as soon as you start to jog, a zone 2 jog may just not be possible right now. Your zones may not be properly calibrated. You need an accurate max heart rate to set your zones properly (more on that below), and an age-based formula is not guaranteed to be correct. You have more important things to do than stick to zones! Your body needs to learn technique, pacing, and all kinds of physical and psychological skills. Every brain cell you spend on obsessing over zones is a brain cell that's not available for the more important tasks before you.Remember, the reason your watch tells you your heart rate is because that's something that is easy for the watch to measure and display—not because it's the most important thing for you to pay attention to. Know that zones are different from app to appThere isn't just one heart rate zone system! There are dozens, if not hundreds. Some have three zones, some four, some five, and some even more. Even when two apps or wearables use a five-zone system, they don't necessarily set the boundaries of the zones in the same places. For example, some systems will set "zone 2" at 60% to 70% of your max heart rate, while others will use 65% to 75%. The different systems also don't agree on what those percentages are of. Sometimes it's maximum heart rate, which we'll discuss below; sometimes it's heart rate reserve, which also takes your resting heart rate into account. Less commonly, you might find zones based around other metrics like lactate threshold. The most common five-zone systemI know you're not going to be happy until you see me set out a chart of numbers, so here goes. This is not the only zone system out there, but it's one that works decently well for most purposes, and you'll find it in several different apps and wearables. It's not the best, but it is perhaps the simplest. You'll need to know your maximum heart rate (MHR), and then you can take percentages of that to know your zones: Zone 1: 50% to 60% of your maximum heart rate (MHR), though some systems will go up to 65%Zone 2: 61% to 70% of MHR; some systems will go up to 75%Zone 3: 71% to 80%, or it might be more like 76% to 85%Zone 4: 80% to 90%, or sometimes 85% to 95%Zone 5: All the way up to 100%In these systems, zone 1 is for warmups or very easy recovery between intervals. Zone 2 is for easy aerobic training, like a light jog—something you could keep up for hours if you're reasonably fit. Zone 3 is for stuff that feels like a medium intensity, like a faster jog, something that would tire you out to do for more than an hour, but you can keep it up pretty steadily. Zone 4 is when things get intense, usually for just a few minutes at a time, and you’ll only bump in zone 5 for a few seconds during your hardest intervals. You can’t sustain work in zone 5 for much longer than that. If it’s a four-zone systemFour-zone systems cover the same general territory, but break it down into fewer, bigger chunks. Usually they do this by combining the first two zones, to give you something like this: Zone 1: anything below 70% (or 75%)Zone 2: 71% to 80% (or sometimes 76% to 85%)Zone 3: 81% to 90% (or 86% to 95%)Zone 4: Everything on up to 100%In these systems, easy-effort endurance work is generally done in zone 1 (instead of warming up in zone 1 and considering the workout itself to be zone 2). Zone 2 is for medium efforts, zone 3 for hard efforts, and zone 4 for absolutely killer, short intervals. How to find your maximum heart rateNow that you know the zones, you’re only missing one thing: your maximum heart rate, which forms the basis for them all. Commonly, these systems will recommend you subtract your age from the number 220 to find your max heart rate. Occasionally they’ll use another formula. But these formulas are often wrong, since they give a single number for everybody at the same age. We're supposed to believe all 43-year-olds have a max heart rate of 177, but in reality there are plenty of 43-year-olds with a max heart rate over 200, and it's not rare to find some 43-year-olds with a max heart rate in the 150s. (Similar caveats apply to any age.) The person with the 200 max will wonder why they're always in "zone 4" when they feel like they're in zone 2, and the person with the 150 max will wonder why they feel like they're dying when they're in "zone 3." So don't rely on a formula, especially if you're seeing zones that don't make sense for how a workout felt. Ideally you’ll do a max heart rate test as I described here, or make an educated guess by looking up the highest heart rate that your device recorded during one of your hardest workouts.What each heart rate zone should feel likeYou can do a little reality check on your zones by making sure they feel right. Here's what they should feel like: Zone 1 will feel very easy, barely like you’re exercising at all. In zone 2, you’ll start to feel hot and sweaty, but you can still easily carry on a conversation. In zone 3, your breathing will get a bit heavier. The lower end of zone 3 is still conversational, but toward the top of this zone you’ll only be able to say a few words at a time. In zone 4, you’re working hard and not in the mood to talk, but you probably feel like you could keep this effort up for a while—or a few more minutes at least. Zone 5 is your absolute top speed, and you can only stand it for a few grueling seconds. If you aren’t sure of your max heart rate, try using this effort-level guide for a while. When you actually do get to a workout that calls for zone 5, give it your all—then check your heart rate monitor to see what number it gave you. How do I stay in zone 2? I have more on zone 2 here, including what it is, how to do it, and why it might be just a teensy bit overrated. Zone 2 refers to an easy effort that you can carry on basically forever. If you're a beginner, walking might be a zone 2 workout. For an athlete, zone 2 might be a brisk jog that they could keep up for a few hours. The best marker of a zone 2 workout is that you stop because time is up, not because you're too tired to continue. There's nothing special about staying in zone 2, except that it's low-fatigue and so you can do a lot of it. If you find your heart rate inching up into zone 3, that's honestly totally fine for probably 99% of people. The more exercise you do, the more you have to pay attention to the intensity of it. Athletes who are exercising 10 hours every week need to make sure that some of those workouts are easy ones. But if you're getting in a few 30-minute jogs or exercises classes, any intensity is fine so long as you end most workouts feeling good and not totally exhausted.