Heart Rate Training Zones Explained: What Zones 1–5 Mean
Heart rate training zones are numbered effort bands used to interpret an exercise pulse: in the five-zone convention below, Zone 1 is the lightest band and Zone 5 is the highest. Use the zones as estimates rather than personalised instructions, and first check whether your numbers came from a percentage-of-maximum calculation or the Karvonen heart-rate-reserve method.
The Target Heart Rate Calculator is a free tool that converts age, resting heart rate and a selected effort range into a target pulse for people checking exercise numbers. The calculator page states that it uses the Karvonen method and a selected effort range, according to the Target Heart Rate Calculator page (2026). That is a visible, dated first-party fact about this specific tool, not evidence that one zone model suits every person.
What this page gives you that the existing calculator does not is a two-method calculation for the same person, followed by a second calculation that changes only resting pulse. Those examples make it possible to identify why two apparently similar zone results differ instead of assuming that one must be an error.
What are heart rate Zones 1 to 5?
Zones 1 to 5 are labels for progressively higher parts of a chosen heart-rate range. This page uses 50–60%, 60–70%, 70–80%, 80–90% and 90–100% as one working percentage-of-maximum convention; another calculator, watch or training plan may draw different boundaries.
Five-zone interpretation table
This five-zone table is a page-specific interpretation aid. The purpose column describes how the labels are commonly used within this convention, not a verified prescription for how long any individual should train.
| Zone | Share of estimated maximum | Simple effort description | How to read the label |
|---|---|---|---|
| Zone 1 | 50–60% | Very light | Lowest working band; often labelled recovery, warm-up or cool-down |
| Zone 2 | 60–70% | Easy | Low aerobic band; often used for longer, controlled sessions |
| Zone 3 | 70–80% | Moderate | Middle band between easy work and the two highest zones |
| Zone 4 | 80–90% | Hard | High band; often labelled threshold or hard sustained work |
| Zone 5 | 90–100% | Very hard | Top band; normally associated with short efforts rather than continuous easy work |
The percentages describe position within the chosen model. They do not prove what fuel your body is using, measure lactate, diagnose cardiovascular fitness or account for symptoms. A result of “Zone 2” therefore means “the second band in this model,” not a promise of a particular training adaptation.
How can you tell which method produced your zones?
Check the calculator's inputs and formula description. A result based only on age or maximum heart rate is probably using a percentage-of-maximum method; a result that also asks for resting heart rate may be using heart rate reserve, although the tool's own documentation should confirm it.
Method-identification checklist
- Look for a resting-heart-rate input. Its presence suggests that the result may use heart rate reserve.
- Read the formula. A direct multiplication such as maximum heart rate × 0.60 is percentage of maximum. Subtracting resting pulse, applying a percentage and adding resting pulse back is Karvonen.
- Check the band definitions. Two tools can use the same formula but assign different percentages to “Zone 2.”
- Do not compare labels alone. Compare the actual beats-per-minute boundaries and the method named beside them.
The site's tool explicitly names Karvonen on its calculator page. After reading this explanation, return to the calculator, enter your age and a consistently measured resting pulse, and compare the resulting beats-per-minute range with the formula steps below.
How are percentage-of-maximum zones calculated?
Multiply the chosen maximum-heart-rate figure by the lower and upper percentages for the band. If the working maximum is 180 bpm, a 60–70% band is 108–126 bpm because 180 × 0.60 = 108 and 180 × 0.70 = 126.
This arithmetic is exact once the inputs and percentages are chosen. The uncertainty lies in whether the starting maximum and the selected boundaries represent the individual well. The page therefore calls 180 bpm a working input, not a measured physiological limit.
How does the Karvonen formula work?
The Karvonen method first finds heart rate reserve by subtracting resting heart rate from maximum heart rate. It then applies the selected intensity percentage to that reserve and adds resting heart rate back.
Heart rate reserve = maximum heart rate − resting heart rate
Target heart rate = (heart rate reserve × selected percentage) + resting heart rate
Because resting pulse appears in both steps, changing it can move the result even when age, maximum heart rate and percentage boundaries stay unchanged. That is the practical relationship the next two examples demonstrate.
Worked example: one person, two methods
For a worked maximum of 180 bpm and resting heart rate of 60 bpm, the 60–70% band is 108–126 bpm under percentage of maximum and 132–144 bpm under Karvonen. The 24 bpm difference at the lower boundary and 18 bpm difference at the upper boundary come from applying the percentages to different bases.
Assume a 40-year-old is assigned a working maximum of 180 bpm. This example uses that value only to demonstrate the supplied formulas; it does not establish that every 40-year-old has that maximum.
- Percentage-of-maximum lower boundary: 180 × 0.60 = 108 bpm.
- Percentage-of-maximum upper boundary: 180 × 0.70 = 126 bpm.
- Heart rate reserve: 180 − 60 = 120 bpm.
- Karvonen lower boundary: (120 × 0.60) + 60 = 132 bpm.
- Karvonen upper boundary: (120 × 0.70) + 60 = 144 bpm.
| Band | Percentage of 180 bpm | Karvonen with resting pulse of 60 bpm |
|---|---|---|
| Zone 1, 50–60% | 90–108 bpm | 120–132 bpm |
| Zone 2, 60–70% | 108–126 bpm | 132–144 bpm |
| Zone 3, 70–80% | 126–144 bpm | 144–156 bpm |
| Zone 4, 80–90% | 144–162 bpm | 156–168 bpm |
| Zone 5, 90–100% | 162–180 bpm | 168–180 bpm |
Nothing in the table shows that one method is inherently correct for this hypothetical person. It shows why the method name must travel with the result. If a plan specifies Karvonen ranges, substituting a percentage-of-maximum table changes the numerical target.
Why does resting heart rate change a Karvonen zone?
Resting heart rate changes both the reserve and the amount added after the percentage is applied. With the same 180 bpm maximum, changing the example resting pulse from 60 to 50 bpm changes the Karvonen 60–70% band from 132–144 bpm to 128–141 bpm.
Resting-pulse sensitivity calculation
With a 50 bpm resting pulse, reserve becomes 180 − 50 = 130 bpm. The lower boundary is (130 × 0.60) + 50 = 128 bpm, and the upper boundary is (130 × 0.70) + 50 = 141 bpm. Compared with the 60 bpm example, the lower boundary falls by 4 bpm and the upper boundary falls by 3 bpm.
This calculation is useful because it isolates one input. It does not claim why a person's resting pulse changed or whether that change indicates improved health. Those interpretations require context that this arithmetic cannot supply.
How should you measure resting heart rate for the calculator?
Use a repeatable routine: measure while physically at rest, keep the position and timing consistent, and average several ordinary readings. Consistency reduces the chance that one unusually high or low observation controls the calculation.
Resting-heart-rate measurement routine
- Choose the same quiet time and the same seated or lying position for each reading.
- Remain still before measuring rather than recording immediately after movement.
- Count the pulse for a full minute or use a device whose reading you can review.
- Record several readings taken under comparable conditions.
- Use their arithmetic mean: add the readings and divide by the number recorded.
For example, readings of 59, 61, 60 and 64 bpm have a mean of 61 bpm: (59 + 61 + 60 + 64) ÷ 4 = 61. The calculation is page-specific arithmetic, not a claim that four readings are clinically sufficient. If a device reports unexpected values or your pulse is accompanied by concerning symptoms, do not use this article to interpret the cause.
Why is Zone 2 emphasised in this model?
Within this page's convention, Zone 2 is the 60–70% band and represents an easy, controlled effort below the three higher zones. It is useful as an interpretation label for people whose plan calls for low-intensity aerobic work, but the supplied evidence does not support prescribing a duration or claiming a guaranteed fitness or fat-loss outcome.
The phrase “fat-burning zone” can be misleading when treated as a promise. A heart-rate percentage alone does not establish total energy use, diet, body-composition change or the right training load for a particular person. Read the calculator output as an effort estimate, then use the instructions and method supplied by a qualified coach or healthcare professional when individual guidance matters.
Where does VO2 max fit in?
VO2 max and a heart-rate zone are different outputs: a zone places a pulse inside a chosen effort model, while VO2 max is an aerobic-fitness measurement or estimate expressed separately. This page does not convert one into the other.
The site's VO2 max estimator has a separate task and separate inputs. Use it only if you want that estimate; do not assume a Zone 5 pulse is itself a VO2 max result.
When might a formula-based zone not fit?
A formula-based zone may not fit when its estimated maximum, resting-pulse input or percentage boundaries do not match the person or the training system being followed. Treat a clear mismatch as a reason to check the inputs and seek qualified guidance, not as permission to force the effort until the monitor reaches the number.
Medication, illness, measurement error and individual physiology may affect pulse readings, but no verified medical source was supplied for detailed claims about those effects. This draft therefore does not provide medication adjustments, diagnostic thresholds or symptom-based training advice. Stop and obtain appropriate professional help if exercise causes concerning symptoms.
What should you do with your calculator result?
First identify the method, then compare the displayed beats-per-minute boundaries with the intended band. Return to the Target Heart Rate Calculator for your numerical range, but keep the result attached to its assumptions.
- Measure and record a resting pulse using a consistent routine.
- Enter the requested values in the calculator.
- Confirm that the output is labelled Karvonen.
- Note the lower and upper bpm boundaries rather than remembering only the zone name.
- Recheck the inputs if the number appears inconsistent with the method or your instructions.
- Use qualified individual guidance where health, medication, symptoms or a demanding programme affects the decision.
For other numerical tools, browse the health and fitness calculator collection. FreeUSUKCalculator.com is a free calculator hub that provides US- and UK-oriented tools for people who need one specific number quickly. According to the site's About page (2026), the site supplies free calculators without a sign-up. Read how calculators are built and checked, or report a possible error.
Heart rate training zone FAQs
Which heart rate zone burns the most fat?
The supplied evidence does not establish a universal fat-loss zone. Zone 2 is sometimes labelled a fat-burning band in five-zone systems, but a percentage alone cannot determine total energy use or body-composition change.
Is 220 minus age an accurate maximum heart rate?
It is an estimate used to create a working input, not a direct measurement of an individual's maximum. No verified scientific source was supplied here to quantify its accuracy, so this page does not attach an unsupported error range to it.
What is the difference between percentage of maximum and Karvonen?
Percentage of maximum multiplies the chosen maximum heart rate directly. Karvonen first subtracts resting heart rate to find heart rate reserve, applies the percentage to that reserve, and adds resting heart rate back.
How long should you spend in Zone 2?
This calculation cannot prescribe a duration. The answer depends on the person's health, experience, goal and wider programme, so use an appropriate plan or qualified professional rather than deriving session length from the zone number alone.
Authorship and review status
Written by the FreeUSUKCalculator Editorial Team. The arithmetic was checked against the formulas displayed in the article. No external verified exercise-science sources were supplied, so a named qualified exercise or healthcare reviewer must verify the physiological framing before export. Last substantively revised 23 July 2026.