40-20 Interval TimerFree 40-20 interval timer for demanding 2:1 ratio HIIT training. 40 seconds work, 20 seconds rest — popular in CrossFit, F45, and circuit training.Frequently asked questionsWhat makes the 40-20 ratio effective for HIIT?The 40-20 ratio (2:1 work:rest) creates high time under tension: across 10 rounds, you do 400 seconds of work and only 200 seconds of rest. The limited 20-second rest keeps heart rate elevated throughout, training the cardiovascular system to perform under sustained metabolic stress. It's more demanding than 30-30 but less extreme than Tabata.Who uses the 40-20 interval timing in fitness classes?40-20 is extremely popular in structured fitness formats: F45 Training, CrossFit AMRAPs, OrangeTheory all-out efforts, boot camp classes. The 40-second work period is long enough to complete meaningful reps and allow complex movement, while the 20-second rest creates urgency and keeps sessions dense.What exercises are best for 40-second HIIT intervals?40 seconds works perfectly for: kettlebell swings, box jumps, rowing machine, battle ropes, dumbbell thrusters, TRX rows, push-up variations, jump rope. The longer work period (vs 20-second Tabata) allows more complex compound movements and full-range exercises like deadlifts and pull-ups at moderate intensity.How many 40-20 rounds should I complete per session?8 rounds = 8 minutes work. 10 rounds = 10 minutes. 12 rounds = 12 minutes. With 2–3 exercises rotating (e.g., a circuit), 12 rounds gives 4 rounds per exercise. Most 40-20 workouts run 20–30 minutes total (including warm-up and cool-down). Add a 1-minute rest between circuits in longer sessions.Is 20 seconds of rest enough in the 40-20 timer?It's intentionally barely enough — that's the point. 20 seconds rest after 40 seconds of hard work keeps your heart rate above 75–80% throughout the session. If 20 seconds feels like plenty, you need to work harder during the 40-second intervals. If you feel sick or dizzy, increase rest to 30 seconds temporarily.