Where the story comes from

Mark Divine served in the US Navy SEALs and wrote about box breathing for Time in 2016. He says he first learned breath control through martial arts during SEAL training, and developed box breathing afterward, to keep up his breath training once he had left the SEALs.1

He describes practicing it in the morning, before a workout, while standing in line and while stuck in traffic, and says that even 5 minutes leaves him calm in body and alert in mind.1

How Divine describes it

Divine starts with empty lungs. Breathe all the air out and hold for 4. Breathe in through your nose for 4, hold for 4, then breathe out smoothly through your nose for 4. That is one cycle, 16 seconds.1

On the holds, he says not to clamp down. Keep an open, expansive feeling even though no air is moving.1

Sit or stand upright, with your feet flat and your shoulders down, and keep the breath quiet. If 4 seconds feels long, start at 3. The timer above starts on the in breath; the cycle is the same.

How long Divine does it

Divine recommends at least 5 minutes at a time. His own routine is one session of 10 to 20 minutes a day, plus 1- or 2-minute "spot drills" whenever the chance comes up. He says it can be done anywhere, as long as you aren't in the middle of a complex task.1

That is one practitioner's routine, and no study has tested it. For a gentler way in, the guide to how long to do box breathing has a 3-week plan.

What the training research shows

Police training has its own names for the pattern. A former Kansas City police officer who now teaches law enforcement describes learning combat breathing, also called tactical or box breathing, on her second day at the academy: in through the nose for 4, hold for 4, out through the mouth for 4, hold for 4.2 Researchers describe tactical breathing as a technique military and law enforcement personnel use to reduce stress and keep performing in dangerous situations.3 The evidence for it is mixed.

A 2025 preregistered study had 96 police students work in pairs through a simulated critical incident. Pairs told to use tactical breathing performed better than pairs told to focus on standard procedure, as judged by expert observers. They did not report feeling less stressed.4 The authors suggest the breathing changed how much attention people had available, with no drop in how stressed they felt.

A 2021 laboratory study compared tactical breathing with prolonged exhalation in 30 healthy people doing a fast Stroop task (naming ink colors) under rising noise. Physiological arousal was lower during tactical breathing, but people performed better with prolonged exhalation, and how stressed they felt didn't differ. The authors suggest tactical breathing may suit situations where you can only wait, and a long exhale those where you have to act. They also note that the evidence for tactical breathing is limited and that other techniques are easier to learn and apply.3

Why it is taught

The 4 equal counts are easy to remember. Divine describes the 4-4-4-4 ratio as neutral: it won't charge you up or make you sleepy, and it leaves him alert and grounded.1

Without the holds, the same counts are equal breathing, 4 in and 4 out. For a slower box, choose Deep Box, 6-6-6-6, on the home page timer.

In the Stanford trial, 21 people did 5 minutes of box breathing a day for a month. Their mood improved against their own starting point, but not significantly more than with mindfulness meditation.5 That is a small, short-term result.

The folklore problem

The story is often told as if box breathing is a hidden SEAL technique with a proven record in combat. The verifiable parts are smaller: a former SEAL named it and writes about using it after his service, police instructors teach a 4-count version, and a handful of studies test tactical breathing with mixed results.1,2,3,4

That leaves a portable practice with a good story attached, which may be why it spread. Treat claims of certainty, in either direction, with suspicion.

Questions

Do Navy SEALs actually use box breathing?

Mark Divine, a former Navy SEAL, says he developed box breathing after leaving the SEALs, building on the breath control he learned in SEAL training.1 We found no public source showing that it is part of official SEAL training.

Does box breathing lower your heart rate?

Not at rest, as far as the Stanford trial could tell: a month of daily breathing practice, box breathing included, didn't significantly change resting heart rate.5 A 2018 review of 15 studies looked at the minutes of practice itself and found that slow breathing, under 10 breaths a minute, raised heart rate variability, the beat-to-beat change in heart rate.6 Box breathing at 4-4-4-4 is about 4 breaths a minute.

Is tactical breathing the same thing?

Often. The police instructor cited above uses combat, tactical and box breathing as names for one 4-count pattern.2 The 2021 study describes tactical breathing as the technique military and law enforcement personnel use to reduce stress in dangerous situations.3

Does box breathing help you focus?

Divine says it slows his breathing and deepens his concentration.1 In the 2025 police study, pairs using tactical breathing performed better in a simulated incident, but that is one study.4

Related timers

This guide isn’t medical advice.

Sources

  1. Divine, M. (2016). A Navy SEAL breathing technique to stay calm and focused. Time.Mark Divine's account of developing and using box breathing, his steps, and how long he practices
  2. Huth, A. (2020). Why you should combat breathe before you leave. Police1, 20 May 2020.Combat breathing, also called tactical or box breathing, taught at a police academy with 4 counts
  3. Röttger, S., Theobald, D. A., Abendroth, J., & Jacobsen, T. (2021). The effectiveness of combat tactical breathing as compared with prolonged exhalation. Applied Psychophysiology and Biofeedback, 46, 19–28.Tactical breathing's use by military and law enforcement personnel, and the 2021 comparison with prolonged exhalation
  4. Sætrevik, B., Granerud, T., Nijhof, M., & Sandvik, A. (2025). Tactical breathing enhances police performance in a critical incident simulation. Collabra: Psychology, 11(1), 144527.The 2025 police student study of tactical breathing and performance
  5. Balban, M. Y., Neri, E., Kogon, M. M., et al. (2023). Brief structured respiration practices enhance mood and reduce physiological arousal. Cell Reports Medicine, 4(1), 100895.The Stanford trial's box breathing arm and resting heart rate
  6. Zaccaro, A., Piarulli, A., Laurino, M., et al. (2018). How breath-control can change your life: a systematic review on psycho-physiological correlates of slow breathing. Frontiers in Human Neuroscience, 12, 353.Slow breathing and heart rate variability during practice