HIIT Interval Calculator
High-intensity interval training (HIIT) is one of the most time-efficient exercise methods available, producing significant cardiorespiratory and metabolic improvements in sessions as short as 10 to 20 minutes. The key variables are work interval duration, rest interval duration, number of rounds, and the total number of sets. This calculator lets you define any work:rest ratio, enter your number of rounds, and instantly see the total session time, total work time, total rest time, and estimated calorie burn. It also shows a simple session structure you can follow, with a warm-up and cool-down recommendation appended to the core interval block.
HIIT session formula
Total intervals = Rounds x Sets
Total work time (s) = Work interval x Total intervals
Total rest time (s) = Rest interval x Total intervals + Set rest x (Sets - 1)
Total session time = Total work + Total rest
Calories = Total work time (min) x Calories per work minute
Frequently asked questions
What is HIIT?
High-intensity interval training (HIIT) alternates short bursts of near-maximal effort with recovery periods. A typical HIIT session lasts 10 to 30 minutes but produces cardiovascular and metabolic adaptations comparable to much longer moderate-intensity sessions, according to research published in peer-reviewed sports science journals.
What is the best work-to-rest ratio for HIIT?
Common ratios are 1:1 (30s work, 30s rest), 1:2 (20s work, 40s rest), and 2:1 (40s work, 20s rest). A 1:1 or 1:2 ratio is appropriate for beginners. More advanced athletes can use 2:1 ratios. The optimal ratio depends on the intensity and goal.
How many HIIT sessions per week is safe?
Most guidelines recommend 2 to 3 HIIT sessions per week with at least 48 hours of recovery between sessions. HIIT places high stress on the cardiovascular and neuromuscular system. More frequent HIIT increases injury and overtraining risk.
How many calories does HIIT burn?
HIIT burns approximately 6 to 15 calories per minute during the work intervals, depending on body weight, exercise type, and intensity. Post-exercise oxygen consumption (EPOC) adds additional calorie burn after the session. This calculator uses an estimate of 10 calories per minute during work intervals as a user-adjustable default.
Is HIIT suitable for beginners?
HIIT can be adapted for beginners using lower intensities and longer rest periods (1:3 or 1:4 ratio). Beginners should start with 10 to 15-minute sessions and build to 20 to 30 minutes over 4 to 6 weeks. Consult a healthcare provider before starting HIIT if you have cardiovascular or joint conditions.
Official sources
- American College of Sports Medicine: ACSM HIIT Position Statement.
- National Strength and Conditioning Association: NSCA Interval Training Guidelines.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.