Zone 2 Calculator
Find the top of your aerobic base from a lactate test — power, pace and heart rate
Zone 2 from your lactate test
Enter your step test — LT1 is the ceiling of Zone 2, and the curve shows where it sits.
Protocol & pre/post values (optional)
Protocol tips — how to enter your test
- Base La= at rest, before test
- Row 1= first workload step
- Lactate column= measured value at sampling time
- Power / HR= intensity of that step
Fill in your lactate test above — the curve and thresholds appear here.
Or load the demo data to see an example.
How to find your Zone 2 from a lactate test
Zone 2 is the intensity just below your first lactate threshold: the hardest effort at which lactate still stays close to its resting level, typically between 1.5 and 2.0 mmol/L. It is where the aerobic system does almost all the work, mitochondria and fat oxidation adapt most, and the session leaves you able to train again tomorrow.
Percent-of-FTP or percent-of-max-heart-rate rules put Zone 2 in roughly the right place for an average athlete and the wrong place for many real ones — a well-trained rider may hold 80 % of FTP at 1.8 mmol/L, a beginner may be past LT1 at 65 %. A step test measures where your own curve starts to rise, and that point is the ceiling of your Zone 2.
Enter the stages of a lactate test and the calculator draws the curve and places LT1 on it. The band below LT1, with its power or pace and the heart rate that went with it, is your Zone 2. A free account turns it into a full zone table you can train from and pushes it to your watch.
Questions
- What should lactate be in Zone 2?
- Steady, and close to baseline — for most athletes 1.5–2.0 mmol/L, rising by less than about 0.5 mmol/L over a long session. If a sample taken 40 minutes in reads clearly higher than one taken at 10 minutes, the pace is above Zone 2 even if it feels easy.
- Can I use heart rate instead of lactate for Zone 2?
- Once you know where LT1 sits, yes: the heart rate at LT1 from the test is the top of your Zone 2 and holds for weeks. Heart rate on its own, from a formula, does not know where your threshold is.
- How long should Zone 2 sessions be?
- Long enough for the aerobic stimulus to accumulate — 60 to 90 minutes for most people, longer for trained endurance athletes. Two to four such sessions a week is the usual base; the intensity is easy on purpose, the volume is the work.
Ready to track your full training load?
LaChart combines lactate testing, training analytics, Strava and Garmin sync and coach collaboration in one place.
