Breath regulator

What box breathing actually is

Box breathing — square breathing, four-square breathing, the same thing under three names — is a paced-breathing pattern in four equal parts: inhale four seconds, hold four, exhale four, hold four. One box takes sixteen seconds, so a minute of it is three and three-quarter breaths, against the twelve to twenty an adult typically takes at rest without thinking about it. Slowing the breath by roughly a factor of four is the entire intervention. There is nothing else in it.

The symmetry is the design, not a flourish. Equal counts give you one number to hold on to, which is why this is the version that ends up in military and emergency-services training: it survives being used by someone who is not thinking clearly. The pacer above is that single number turned into a shape, so you can follow a ring instead of counting in your head while also trying to breathe.

It is worth being blunt about what the tool is. It is a metronome. It has no camera, no microphone and no sensor of any kind, so it cannot tell whether you are breathing with it, breathing shallowly, or reading this paragraph and ignoring it entirely. It sets a pace, labels the current phase, and counts the cycles it has drawn. Everything that happens in your body is happening on your side of the screen.

The four patterns, and how they differ

Each option in the picker is a list of seconds — inhale, hold, exhale, hold — and a zero means that phase is skipped entirely rather than shortened.

• Box · 4-4-4-4. Sixteen seconds a cycle, 3.75 breaths a minute, everything equal. The plain version, and the one to start from if you do not have a reason to pick another.
• Calm · 4-7-8. Inhale four, hold seven, exhale eight, no closing hold. Nineteen seconds a cycle, about 3.2 breaths a minute — the slowest of the four and much the most demanding, because of the seven-second hold stacked in front of an eight-second exhale. This is the pattern popularised by Andrew Weil. If you are new to paced breathing it is the one most likely to feel like a strain, and a strain is a signal to switch to a shorter pattern rather than to push through.
• Coherence · 5-5. Inhale five, exhale five, no holds at all. Ten seconds a cycle — exactly six breaths a minute, which is the rate most heart-rate-variability work is built around, for the reason set out two sections down. It asks the least of you of the four, and it is the one to use if holding your breath is uncomfortable or you have any reason to avoid it.
• Unwind · 4-2-6. Inhale four, hold two, exhale six. Twelve seconds a cycle, five breaths a minute, with the exhale half again as long as the inhale. This is the cheapest way to get the extended-exhale shape without the length of 4-7-8.

So: two of the four make the out-breath longer than the in-breath, box makes every phase equal, and coherence makes them equal while removing the holds. Those are real differences in what you are being asked to do, and the next section is about the one that matters most.

Why the exhale being longer than the inhale is the point

Heart rate is not constant across a single breath. It rises while you inhale and falls while you exhale, every breath, all day — a normal, measurable oscillation called respiratory sinus arrhythmia. The standard account of it is that the vagus nerve's braking influence on the sinoatrial node is reduced during inspiration and restored during expiration, so the heart is released and re-braked once per breath. You can watch this on any ECG trace; it is not a subtle or contested effect.

A pattern with a longer exhale than inhale spends a larger fraction of each cycle in the half where that braking influence dominates. That is the mechanism the extended-exhale patterns are reaching for, and it is the reason 4-7-8 and 4-2-6 are shaped the way they are rather than being arbitrary numbers.

That is a mechanism, and this page stops there on purpose. What is well established is the physiology: the oscillation is real, it is measurable, and it tracks the breath. What any particular person notices after three minutes of paced breathing varies enormously, and nothing on a web page can tell you in advance what you will notice. If you want a claim about how you will feel, this is the wrong page; if you want to know what the pattern is doing and why it is shaped that way, that is what is written down here.

What the “six breaths a minute” figure refers to

Six breaths a minute means one full breath every ten seconds, or 0.1 Hz, and it keeps turning up in the literature for a structural reason rather than because six is a special number.

Blood pressure is regulated by the baroreflex, a feedback loop with a built-in lag of roughly five seconds: pressure is sensed at the carotid and aortic baroreceptors, heart rate is adjusted, pressure responds, the loop goes round again. A feedback loop with a ~5-second delay is most responsive when it is driven at about a ~10-second period, and breathing at six a minute drives it at exactly that. The respiratory oscillation and the baroreflex oscillation line up in phase, and the result is the largest swing in heart rate the system will produce. That swing is what shows up as raised heart-rate variability in the short recordings paced-breathing and HRV-biofeedback protocols use.

Two caveats that are usually left out. First, the resonance rate is individual: measured resonance frequencies in adults typically land somewhere between about 4.5 and 6.5 breaths a minute, and the first session of a proper HRV-biofeedback course is usually spent finding a person's own. The Coherence 5-5 option here is a reasonable average, not your number, and this page has no way to measure your number. Second, raised variability during a paced session is a description of what your heart is doing while you pace your breathing. It is a physiological measurement. It is not a mood, not a diagnosis, and not a result.

How to use the pacer

Sit or stand with your shoulders down and put a hand on your stomach. If only your chest is moving, you are breathing high; the belly should move first. Press Start, then follow the ring rather than leading it — the common mistake is to race slightly ahead of the animation, which turns a slow-breathing exercise into a slightly-faster-breathing exercise. Two or three minutes, somewhere between ten and twenty cycles, is an ordinary session; the counter under the ring tells you where you are.

Breathe slower, not bigger. If you are pulling in large volumes of air to fill four seconds, the pattern is too long for you and the answer is a shorter one, not more effort. This is also where the warning under the ring comes from: moving more air than your body needs clears carbon dioxide faster than you produce it, and a fall in blood CO₂ narrows the arteries supplying the brain, which is what the light-headedness and the tingling in the fingers are. Stop, let your breathing go back to normal, and use a shorter pattern next time.

Switching patterns mid-session restarts the current cycle; Reset clears the counter and returns the ring to Ready. The count is driven by the wall clock rather than by a frame counter, so a phase that started four seconds ago is four seconds old even if the tab was busy in between — but a backgrounded tab stops redrawing, so if you switch away and come back the label catches up rather than having quietly kept animating.

When a pacer is the wrong tool

You cannot pace your way out of a situation you should leave. If your body is on alert because of something that is still happening — a conversation going badly, a deadline you are going to miss, a room you are not safe in — slow breathing changes what your cardiovascular system is doing and changes nothing whatsoever about the cause. Sometimes a body on alert is right, and the useful response is to act on what it is alert about. A breathing exercise used to make an intolerable situation tolerable for longer is being used against you, and no amount of 4-4-4-4 fixes that.

• Not while driving or operating machinery. Holding your breath while watching an animated ring needs attention you do not have spare.
• Not if the holds are uncomfortable. Use Coherence 5-5, which has none. There is no version of this where forcing a breath-hold is the point.
• Not as a measurement. This is a timer. If you want to know what your heart rate variability is doing you need a device that measures it, and this is not one.
• Not in a crisis. Nothing on a web page is a crisis service. If you are in danger or thinking about harming yourself, contact your local emergency number or a crisis line now.

What this page is not

This is a breathing timer with an essay attached. It is not therapy, not treatment, not a diagnosis, and not a substitute for care you are already receiving or should be receiving. It does not know anything about you and it makes no attempt to.

Slow paced breathing is one of the more heavily studied self-regulation techniques, and it is also one where the reported effects are modest and are measured mostly over minutes rather than months. This page therefore describes the patterns, the arithmetic and the physiology, and deliberately does not tell you what any of it will do for you — not because the answer is secretly bad, but because the honest answer is that nobody can tell you that from here.

What happens on your device

Nothing here is stored and nothing is uploaded. The pacer is about ninety lines of JavaScript inside main.js, served unminified from this domain so you can read it; the completed-cycle count lives in the page's memory and is gone the moment you press Reset or close the tab. Unlike the focus timer, nothing about your breathing is written to your browser's storage — there is no key to delete, because there is no key. The one network request this page makes is a self-hosted page-view counter that records the URL and nothing else, and /privacy.html lists every storage key the site writes anywhere.

The page is also precached by a service worker, so once you have loaded it once the pacer keeps working with no connection at all — on a train, on a plane, in a basement.

Related tools and reading

The tools page lists the rest: a five-step ACT thought-defusion exercise, a CBT thought record with seven columns you can fill in and export, and a focus-session interval timer. The field guide covers the psychology underneath all four in plain language — predictive processing, the standard list of cognitive distortions, defusion and the observing self, and the physiology of slow breathing — including a section on where the evidence is thin.