🔥 Anaerobic Threshold Calculator
Input results from a field test or lab assessment to find your lactate threshold and personalize heart rate zones.
Average heart rate from minutes 10–30 of the test.
Threshold HR
165 bpm
Lactate threshold heart rate
% of Max HR
86.8%
Typical range 80–92%
% of HR Reserve
81.5%
Karvonen method reference
| Training Zone | % HRR | Heart Rate Range (bpm) |
|---|---|---|
| Recovery (Zone 1) | 50% – 60% | 123 – 136 bpm |
| Endurance (Zone 2) | 60% – 70% | 136 – 150 bpm |
| Tempo (Zone 3) | 70% – 80% | 150 – 163 bpm |
| Threshold (Zone 4) | 80% – 90% | 163 – 177 bpm |
| VO₂ / Anaerobic (Zone 5) | 90% – 105% | 177 – 197 bpm |
How to Use This Calculator
Choose your testing method
Select between 30-minute, 20-minute, or lab-based lactate testing protocols.
Enter test heart rate
Use your average heart rate from the chosen test to anchor threshold calculation.
Provide resting & max heart rate
Resting heart rate determines heart rate reserve; max heart rate can be measured or estimated.
Apply personalized zones
Use the output to structure workouts around recovery, tempo, threshold, and VO₂ sessions.
Formula
Threshold HR = Test HR × Adjustment (method dependent)
Threshold % Max = (Threshold HR ÷ Max HR) × 100
Threshold % HRR = ((Threshold HR − Resting HR) ÷ (Max HR − Resting HR)) × 100
30-minute tests use the average heart rate from the final 20 minutes. 20-minute tests apply a 95% multiplier to approximate functional threshold heart rate (FTHR). Lab tests use the lactate deflection point directly.
Example
20-minute test average HR: 174 bpm → Threshold ≈ 165 bpm. Max HR 190, Resting 55 → Threshold = 86.8% of max, 77.5% of HR reserve. Zone 4 range ≈ 158–169 bpm.
Variables
- Test HR: Field or lab data point
- Adjustment: Method-specific multiplier
- Resting/Max HR: For heart rate reserve calculations
Understanding Anaerobic Threshold
Anaerobic threshold (also called lactate threshold or functional threshold heart rate) marks the intensity where lactate production outpaces clearance. Training around this point builds endurance and sustainable speed.
Why It Matters
- Predicts race performance for endurance events from 10k to marathons and long cycling time trials.
- Guides pacing strategies for tempo, threshold intervals, and sweet-spot workouts.
- Provides individualized training zones that reflect current fitness, not generic formulas.
Improvement Tips
- Perform weekly threshold intervals (e.g., 3×10 minutes at 95–100% of threshold heart rate).
- Include tempo runs or sweet-spot rides to accumulate time just below threshold.
- Retest every 6–8 weeks to adjust zones as fitness evolves.
Frequently Asked Questions
How often should I retest?
Every 6–8 weeks or whenever training load changes significantly. Consistency helps track progress.
Do I need a lab test?
No. Field tests are accurate enough for most athletes, though lab tests provide more detailed physiological data.
Can I use power or pace instead?
Yes—pair heart rate threshold with functional threshold power (cycling) or pace (running) for cross-referenced training zones.
What affects threshold heart rate?
Temperature, hydration, fatigue, and altitude can shift heart rate. Use trends over time rather than single-day values.
Why include resting heart rate?
Heart rate reserve-based zones account for individual cardiac range, leading to more personalized intensity targets.