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Target heart rate calculator
Put your age and resting heart rate in: at age 40 with a 70 bpm resting rate, the maximum is 180 bpm and the target zone is 125 to 163.5 bpm.
★ HEALTH · FITNESS · HEART RATE
Target Heart Rate Calculator: 125 to 163.5 bpm at 40
On the defaults — age 40 with a resting rate of 70 bpm — the target heart rate zone is 125 to 163.5 bpm, from a maximum of 180 bpm and a reserve of 110 bpm. This is the target heart rate tool: subtract age from 220 for the maximum, subtract the resting rate for the reserve, and take 50 to 85 percent of the reserve back above the resting rate — a pulse target guessed from age alone ignores the fittest number you own, your resting rate.
What does 125 to 163.5 bpm, maximum 180 bpm mean?
It means a 40-year-old whose heart rests at 70 bpm has a predicted maximum of 180 bpm, a reserve of 110 bpm between rest and maximum, and a moderate-to-vigorous training zone of 125 to 163.5 bpm. The age sets the maximum, the resting rate sets the reserve, and the percentages set the zone: 50 percent of the reserve above rest is the gentle end, and 85 percent is the hard end. The only judgement is the resting rate — counted first thing in the morning, before coffee and before the day, it is the truest number in the whole calculation, and a resting rate taken after stairs is not a resting rate at all.
Output · formula · meaning
| Output | Formula | What it means |
|---|---|---|
| Maximum heart rate | 220 − age | 180 bpm — 220 − 40. |
| Heart rate reserve | maximum − resting | 110 bpm — 180 − 70. |
| Target low | reserve × 0.5 + resting | 125 bpm — 110 × 0.5 + 70. |
| Target high | reserve × 0.85 + resting | 163.5 bpm — 110 × 0.85 + 70. |
Three things to check before you trust the number
First, check the resting rate honestly: count it lying down, first thing in the morning, for a full minute, on two or three mornings — a rate taken after coffee, after stairs, or after an argument is a working rate wearing a resting label. Second, check the age against the formula’s limits: 220 minus age is a population estimate, and trained athletes often exceed it while unfit people may never reach it — the zone is a guide, not a ceiling with legal force. Third, check the zone against how the effort feels: a zone that leaves you unable to speak is harder than moderate, and a zone that leaves you singing is easier than vigorous — the talk test beats the arithmetic when they disagree.
Worked example
Age 40, resting 70 bpm. Maximum: 220 − 40 = 180 bpm. Reserve: 180 − 70 = 110 bpm. Low: 110 × 0.5 + 70 = 125 bpm. High: 110 × 0.85 + 70 = 163.5 bpm. In practice that means a 40-year-old at rest at 70 bpm should aim for 125 bpm at the gentle end of a workout and up to 163.5 bpm at the hard end — the range to hold on a watch during a run, and the range to quote when a training plan asks for moderate to vigorous effort.
Every branch, checked
At age 30 instead of 40, the maximum rises to 190 bpm, the reserve to 120 bpm, and the zone to 130 to 172 bpm. With a resting rate of 60 bpm instead of 70, the maximum stays 180 bpm but the reserve rises to 120 bpm, and the zone becomes 120 to 162 bpm. At age 50 instead of 40, the maximum falls to 170 bpm, the reserve to 100 bpm, and the zone to 120 to 155 bpm. With a resting rate of 80 bpm instead of 70, the maximum stays 180 bpm but the reserve falls to 100 bpm, and the zone becomes 130 to 165 bpm.
The reverses, worked backwards
The age behind 125 to 163.5 bpm is 40: at age 30 the zone is 130 to 172 bpm (maximum 190, reserve 120); at age 50 it is 120 to 155 bpm (maximum 170, reserve 100). The resting rate behind 125 to 163.5 bpm is 70 bpm: at 60 bpm the zone is 120 to 162 bpm (maximum 180, reserve 120); at 80 bpm it is 130 to 165 bpm (maximum 180, reserve 100) — the resting rate never touches the maximum, only the reserve and the zone.
What the defaults assume
The defaults assume a healthy 40-year-old with a 70 bpm resting rate and no medication that changes heart rate. They do not assume a trained athlete, whose maximum often exceeds 220 minus age; a heart condition; or beta-blockers and similar medicines, which cap the heart rate — any of those needs a clinician’s zone, never the formula’s.
Who uses this
- A runner setting a training zone: the 125 to 163.5 bpm range settles the watch targets before the run.
- A walker starting an exercise plan: the gentle end of the zone is the line for the first weeks, not a guess.
- A coach checking an athlete’s effort: the reserve figure off the calculator is the line to compare across athletes.
- A gym-goer reading a cardio machine: the zone translates the machine’s age-only guess into a personal range.
Accuracy & limitations
The arithmetic is exact for the inputs entered; the judgement is the formula and the resting rate. The 220-minus-age maximum is a population average with wide individual variation, and the Karvonen percentages are training conventions, not measurements — so treat 125 to 163.5 bpm as the planning zone for a healthy 40-year-old at 70 bpm resting, and check it against perceived effort and, where it matters, a clinician’s guidance.
Cite this calculator
Bright Side Kit, “Target Heart Rate Calculator: 125 to 163.5 bpm at 40”, https://brightoolbox.com/target-heart-rate-calculator/, accessed 3 November 2026. Students and researchers: cite the calculator name, the page URL and the date you used it, and quote the defaults (age 40, resting 70 bpm) so the result can be checked.
Frequently asked questions
What is my target heart rate at age 40?
125 to 163.5 bpm on the defaults: a maximum of 180 bpm, a reserve of 110 bpm above a 70 bpm resting rate, with 50 percent giving 125 bpm and 85 percent giving 163.5 bpm.
How do I measure my resting heart rate?
Count it first thing in the morning, lying down, before coffee, for a full minute, on two or three mornings and take the lowest. A rate taken later in the day is not a resting rate.
Why does the resting rate matter?
Because the zone is built on the reserve between rest and maximum: a lower resting rate leaves a bigger reserve, which lifts both ends of the zone. Age alone ignores fitness, and the resting rate is where fitness enters the maths.
What does 50 to 85 percent mean in practice?
Roughly moderate to vigorous effort: at 50 percent you can talk in short sentences, and at 85 percent talking is hard. The percentages are the training convention behind most cardio plans.
Can I exceed my predicted maximum?
Yes, often: 220 minus age is an average, and trained people regularly exceed it. Exceeding it does not mean the calculator is broken, only that you are fitter than the average for your age.
Is this medical advice?
No: it is a training-planning figure for a healthy adult. A heart condition, medication that affects heart rate, or any cardiac symptom all override it — ask a clinician for your zone in those cases.