Start from a threshold pace, a recent race or a goal time and get the five zones your running should be done in: easy, aerobic, tempo, threshold and VO2max. Add your FTP for bike power zones and a swim time trial for critical swim speed. These are the zones the Endurance by Design app puts on every workout card.
| Zone | Pace / mi | Pace / km | What it is for |
|---|
Endurance by Design puts your threshold-anchored paces on every run card, your watts on every bike block, and recalibrates them from a fitness check in your first eligible week. Free to download, 7-day free trial.
Every zone hangs off one number: threshold pace, the pace you could hold for about an hour. The five run zones are fixed multiples of it, slowest to fastest. This is the threshold-anchored model the Endurance by Design engine adopted after its methodology review, and it is why zone 4 means threshold whether you are training for a 5K or an IRONMAN.
| Zone | Multiple of threshold pace | Example at 7:46 / mi threshold | What it is for |
|---|---|---|---|
| 1 Recovery and easy | 1.35 to 1.22 | 10:29 to 9:28 / mi | Warm-ups, recovery runs, the easy half of long runs |
| 2 Aerobic base | 1.22 to 1.11 | 9:28 to 8:37 / mi | Most weekly minutes; comfortable but purposeful |
| 3 Tempo | 1.11 to 1.03 | 8:37 to 8:00 / mi | Marathon pace, steady state, long-run finishes |
| 4 Threshold | 1.03 to 0.97 | 8:00 to 7:32 / mi | Cruise intervals and threshold runs |
| 5 VO2max | 0.97 to 0.88 | 7:32 to 6:50 / mi | 5K pace and faster; short hard intervals |
If you enter a race or a goal instead of a threshold, it is projected to a one-hour effort first:
one-hour distance = race distance × (3600 ÷ race seconds)1 ÷ 1.06 · threshold pace = 3600 ÷ one-hour distanceA 1:45:00 half marathon projects to 4:49 per km, or 7:46 per mile, which is the example in the table. A 3:45:00 marathon projects to 4:57 per km, and that runner's marathon pace of 5:20 lands in zone 3, the tempo band, which is where marathon pace belongs.
Bike zones are shares of Functional Threshold Power. The midpoints are 50, 66, 83, 98 and 113 percent of FTP, so a 250 W FTP gives targets of 125, 165, 208, 245 and 283 W. Swim training is anchored on critical swim speed, your threshold per 100 m. From a 400 m and a 200 m time trial swum fresh on the same day, CSS is the difference between the two times divided by two: a 6:40 and a 3:10 give 1:45 per 100 m.
Updated October 21, 2026
About 22 to 35 percent slower than your threshold pace. For a runner with a 7:46 per mile threshold, easy runs sit between 9:28 and 10:29 per mile. If you can only speak in short phrases, you are above easy.
Because threshold means the same effort for everyone, roughly an hour at the limit, at every distance. Zones set from goal race pace drift: a 5K runner's threshold would come out as 5K pace, which is too fast. Anchoring on threshold puts marathon pace in the tempo zone and 5K pace in zone 5, where coaches and the research place them.
Enter a recent race instead. The calculator projects it to a one-hour effort using the same formula the race time predictor uses. A 10K or half marathon from the last three months gives the most reliable threshold.
As shares of your Functional Threshold Power: the midpoint of each zone sits at 50, 66, 83, 98 and 113 percent of FTP. The app prescribes a single target wattage per block from these midpoints, which is what the table shows.
CSS is the pace per 100 m you could hold for a long steady swim, the swimming equivalent of threshold. From a 400 m and a 200 m time trial it equals the difference between the two times divided by two, per 100 m.
Every eight to ten weeks in a serious training block, or after any race. Thresholds drift with fitness, and stale zones make easy days too hard and hard days too easy.
Endurance by Design builds your plan around your race and your week, prints these zones on every session, and adjusts them as your fitness moves. Free to download on the App Store, with a 7-day free trial.
