Your race time is used to estimate your current fitness, and each zone is set at the right effort from there. Zones 3 and 4 sit close together. Tempo / Sub-Threshold is a little easier so you can do more of it, while Threshold is the harder effort you could hold for about an hour.
RPE is how hard the effort feels on a scale of 1 to 10. The % value is the percent of your current capabilities, calculated from your race or time trial. The % runs higher than the RPE because even easy running uses most of your engine. Easy running is supposed to feel much easier than your engine is working.
The dashed 5K and 2-Mile race pace lines sit just above the Interval zone, with the faster 2-Mile just below the 5K. Both events are raced at around Interval / VO2 effort, so everything above the lines is slower than race effort.
* When the anchor race is not that distance, the line shows the matching pace for your fitness. Treat the zones as target ranges, not exact lines, and adjust for heat, hills, and tiredness.
This is an independent tool. The pace zones come from running science equations that have been published for decades and over 1,000 cross-referenced racing records and are not connected to any commercial pace product.
This is very easy running. You can talk the whole time or even sing, and your breathing barely changes. Your legs feel light and loose, and it should almost feel too slow. Recovery runs help your body bounce back from hard days without making you any more tired.
This is your everyday pace. You can talk in full sentences without gasping, your breathing is a little deeper but steady, and your legs feel relaxed like you could keep going. Easy running builds your endurance and a stronger heart, so most of your running should happen here.
This feels comfortably hard but still in control. You can only get out a few words at a time, your breathing is deeper and quicker, and your legs are working without any real burning yet. Because it sits just below your hard effort, you build a lot of fitness here without wearing yourself out.
This is hard but steady, right at the edge of what you can hold. You can manage a word or two, your breathing is deep and fast, and your legs have a steady burn you could handle for about an hour in a race. Training here raises the effort you can hold for a long race, so you can race faster before you slow down.
This is very hard. You can maybe get out one word, your breathing is all out, and your legs are burning and heavy after just a few minutes. You run it in short reps with rest in between because you cannot hold it for long, and it builds your top speed and your engine.
This is fast and smooth. The reps are short, so even though you cannot really talk, your breathing comes back fully between them. Your legs feel quick, springy, and powerful, with fast smooth turnover. This trains your speed and running form, so you stop while you still feel sharp instead of worn out.
These are your cross country races: two miles for middle school and a 5K for high school. Both are full race efforts run near the top of your zones, which is why their lines on the calculator sit up around Zone 5. Here is what each one feels like, so you can recognize the effort without staring at a watch. On a course, hills and footing change your pace constantly, so the effort is what you run by.
This is the middle school cross country race, a fast, hard effort that you hold over the full two miles. Your breathing is deep and quick almost from the start, and you can only get a word or two out. Your legs carry a burn that builds steadily the longer you go, and the effort keeps climbing even when your pace stays the same. It feels controlled early and like a real grind by the end, sitting right on the edge of what you can hold the whole way. On a course, hills and soft ground will slow your pace while the effort stays the same, so run the feel and let the pace be whatever it is.
This is the high school cross country race, a strong, sustained effort that is a touch slower than your 2-mile but lasts longer. It starts out comfortably hard and slowly turns hard. Your breathing is deep and rhythmic, you can manage only short words, and your legs go from working to burning over the miles. The same effort feels tougher the longer you hold it, so it takes more and more focus to stay there, and by the final stretch it becomes an all-out grind that leaves you spent. Hills, mud, and grass all make a course slower than the track, so expect the pace to move around while the effort holds steady.