HIIT Interval Timer Calculator
Calculate total HIIT workout time from work duration, rest duration, and number of rounds.
Returns total time, work-to-rest ratio, and calorie burn.
Interval training alternates periods of high-intensity effort with rest or low-intensity recovery. It is one of the most efficient methods for improving cardiovascular fitness, speed, and calorie burn in less time than steady-state cardio.
Core formula: Total Session Time = (Work + Rest) × Rounds × Sets + (Set Rest × (Sets − 1))
Where:
- Work = duration of each high-intensity effort (seconds)
- Rest = recovery time between efforts (seconds)
- Rounds = number of work-rest cycles per set
- Sets = number of sets in the session
- Set Rest = longer recovery between sets (seconds)
Common interval protocols:
| Protocol | Work | Rest | Ratio | Use Case |
|---|---|---|---|---|
| Tabata | 20 s | 10 s | 2:1 | Peak anaerobic power |
| HIIT standard | 30 s | 30 s | 1:1 | General fitness |
| Sprint interval | 10 s | 50 s | 1:5 | Max speed development |
| Aerobic interval | 3 min | 3 min | 1:1 | VO₂ max improvement |
Work-to-rest ratio matters most:
- 1:1 ratio → taxes both aerobic and anaerobic systems equally
- 1:2 or 1:3 ratio → allows fuller recovery, supports higher peak output
- 2:1 ratio (Tabata) → accumulates maximal metabolic stress in 4 minutes
Worked example: A cyclist performs 8 rounds of 40-second sprints with 20 seconds rest, for 3 sets with 2 minutes between sets.
Total = (40 + 20) × 8 × 3 + (120 × 2) = 1,440 + 240 = 1,680 seconds (28 minutes)
Heart rate targets: Work phase should reach 80–95% of max HR. Rest phase should allow recovery to 60–70% before the next interval begins. Monitoring this ratio ensures productive training without overtraining.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
SuperGlobalCalculator is independently built and maintained. See how we build and verify our calculators.