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About this tool
Plan HIIT heart-rate zones, recovery bands and session intensity targets from max heart rate or training threshold.
Interval training is defined by two heart rate numbers — how hard the work interval is and how far your heart rate is allowed to fall before the next one — and this calculator produces both from your age or a measured maximum heart rate. It carries the published formats sessions are copied from: 4 × 4 minutes at 90–95% of maximum with 3 minutes of active recovery, Tabata's 20 seconds on and 10 seconds off for 8 rounds, Billat's 30/30, and 30-second sprint intervals with 4-minute recoveries. It also totals the block, the time actually spent at intensity, and the whole session including warm-up and cool-down.
Open Heart Rate Zones HIIT on AltFTool — it loads instantly in your browser.
Enter the values you already know.
Fine-tune the options to match your scenario.
Read the result and use it in your planning or reporting.
4 × 4, Tabata, 30/30 and sprint intervals with the repetitions, work and recovery each was studied at.
Both numbers in bpm, because an interval session is only as good as its recoveries.
Time at intensity, block length and total session time, so it fits the time you have.
Aerobic intervals of two to five minutes target 90–95% of maximum heart rate, with recovery falling back to about 60–70%. For a 45-year-old with a Tanaka maximum of 177 bpm, that is roughly 159–168 bpm of work and 106–124 bpm of recovery.
The interval block is 25 minutes: four four-minute efforts separated by three three-minute recoveries. Adding a 10-minute warm-up and a 5-minute cool-down brings the whole session to 40 minutes, with 16 minutes spent at intensity.
Heart rate takes 30 to 60 seconds to respond, so a 20-second effort is over before it catches up. Across eight rounds the rate climbs steadily because 10 seconds of rest is not enough to recover, and it usually peaks near maximum in the last rounds. Judge short intervals by power or pace, not by the number on the strap.
Most training plans place two, occasionally three, hard interval sessions in a week with easy work in between, because the limiting factor is recovery rather than willingness. High-intensity training is demanding on the cardiovascular system — if you are new to exercise, pregnant, or have heart disease, high blood pressure or symptoms during exertion, speak to a doctor before starting.
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