Threshold tool

Lactate Threshold Calculator

Estimate lactate threshold from field tests, then determine LTHR, threshold power, or threshold pace for training.

THRESHOLDS
LTHR
Heart rate
FTP
Power
T-PACE
Pace

What is lactate threshold?

Lactate threshold is a practical marker for the effort you can sustain before fatigue rises quickly. This lactate threshold calculator helps you estimate lactate threshold from field tests, then determine LTHR for heart rate, threshold power for cycling, and threshold pace for running. Use repeatable protocols and compare trends, not isolated tests.

Calculator

Choose a metric and enter the data from your test.

Inputs
Choose a metric (heart rate, power, or pace) and enter your test data.
Metric
Use the average heart rate from a steady 20-minute time trial (running/cycling).
20-minute average heart rate
Enter average bpm from a strong but sustainable 20-minute effort.
These are practical field estimates. Use repeatable conditions and track changes over time.
Results
Enter test data to see your threshold.
Choose a metric and enter valid numbers to calculate.
Explained
What these thresholds represent and how to use them.
LTHR (heart rate threshold)
A practical proxy for the heart rate you can sustain around threshold. Often used to set HR zones.
FTP (power threshold)
An estimate of the highest power you can sustain for about an hour. Useful for setting power zones.
Threshold pace
A hard, steady pace you can sustain for a threshold-style effort. Useful for tempo and threshold training guidance.

How to estimate lactate threshold

1

Choose the threshold type

Pick heart rate, power, or pace depending on the field test you completed and the training target you want to determine.

2

Enter repeatable test data

Use a consistent test protocol and similar conditions so you can estimate lactate threshold again later and compare the trend.

3

Update zones gradually

Use the output to refresh LTHR, threshold power, or threshold pace, then check it against real workout feel and recovery.

FAQ

What is lactate threshold?
Lactate threshold is the highest intensity you can sustain before fatigue accumulates quickly. In training it is a practical marker for heart rate, power, and pace—not a lab blood-lactate curve. This calculator estimates that field-test proxy so you can set zones and compare trends.
How do I estimate or determine lactate threshold from a field test?
Pick one metric, then use a repeatable protocol: a 20-minute effort for LTHR, a 20-, 8-, or 60-minute test for threshold power, or a hard time-trial for threshold pace. Enter the average result to estimate lactate threshold. Determine lactate threshold again with the same protocol when you re-test.
How is LTHR different from max heart rate?
LTHR is a sustainable threshold heart rate. Max heart rate is the highest rate you can reach in a short all-out effort. They are not interchangeable: LTHR sits well below HRmax and is better for tempo and threshold work. Use a max heart rate calculator for HRmax, then this tool to estimate LTHR from a field test.
How does this relate to FTP?
FTP is a common cycling name for threshold power. This page estimates that field-test proxy from a timed effort (20-min × 95%, 8-min × 90%, or 60-min). It does not analyze an uploaded activity file. If you want FTP from a GPX, FIT, or TCX file, use the FTP calculator.
How accurate is a field-test lactate threshold estimate?
A field test estimates lactate threshold; it is not a lab blood-lactate measurement. Accuracy depends on pacing, freshness, protocol, and conditions. Use the same test and similar conditions, then trust trends more than a single number.

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