Heart Rate Drift
Calculator
Results
- Heart rate drift (%)
- 6
- Heart rate drift (bpm)
- 9
Endurance training results
| Heart rate drift (%) | 6 |
| Heart rate drift (bpm) | 9 |
formula-map diagram
- Heart rate drift (%)
- 6
- Heart rate drift (bpm)
- 9
Formula breakdown
Formula
Drift % = (HR2 − HR1) ÷ HR1 × 100= 6
Note
Simplified model: these are standard endurance-training formulas (Riegel, ACSM, Banister TRIMP, ACWR, Minetti gradient cost and published fuelling rates) applied to the numbers you enter. They assume even effort, typical conditions and average physiology, and ignore terrain, heat, wind, sleep, individual sweat and carbohydrate tolerance, and training history, so results are indicative planning figures, not medical or coaching advice.
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See all →Frequently asked questions
What does heart rate drift measure?+
It measures the rise in heart rate over time at a constant pace, expressed as a percentage increase between the first and second half of a steady effort. A well-conditioned aerobic system shows minimal drift, since the heart doesn't need to work progressively harder to sustain the same output.
How is the percentage calculated?+
The formula compares average heart rate in the second half of an effort to the first half: drift % = ((second half average HR ÷ first half average HR) − 1) × 100. A positive percentage means heart rate rose relative to pace over the course of the run.
What level of drift is considered healthy versus a red flag?+
Under about 5% drift at a steady aerobic pace is generally considered a sign of good aerobic fitness and adequate hydration and pacing, while drift above 10% often signals the pace was too fast for a true aerobic effort, dehydration, heat stress, or inadequate aerobic base.
What causes heart rate to drift even at the same pace?+
Cardiovascular drift happens as the body redirects blood flow to the skin for cooling, reduces plasma volume through sweat loss, and accumulates fatigue, all of which force the heart to beat faster to deliver the same oxygen and maintain blood pressure at the same running speed.
How can I use drift data to guide my training?+
Consistently high drift at your intended easy pace suggests you should slow down to stay in a true aerobic zone, since exceeding aerobic threshold undermines the base-building purpose of easy runs. Tracking drift over months is also a useful, low-cost way to monitor aerobic fitness improvements without a lab test.