Three important breathing variables are speed, volume, and ratio. My unconscious ‘breathing app’ controls all three. However, I can also decide to manage them intentionally.

Breathing speed

My unconscious breathing speed at rest is the number of breathing cycles I complete in one minute when I’m physically inactive and relaxed. It’s known as “Breathing rate at rest.”

The average breathing rate at rest of a healthy person is 12 to 18 breaths per minute. This rate can slow down or speed up slightly from moment to moment, but it usually stays within the margin of 12 to 18 breaths per minute. Men tend to breathe at rest slightly slower than women.

My breathing rate at rest is one of the four main ‘life vital signs.’ The other three are heart rate, blood pressure, and body temperature. All four affect one another in different ways.

When I start activating my body, my ‘breathing app’ increases my breathing rate so that my muscles get the extra Oxygen required for cellular burning. In this case, my breathing rate may go as high as 60 breaths per minute.

When necessary, I can take control of my ‘breathing app’ and intentionally decide to breathe faster or slower than my breathing rate at rest.

Important: My bloodstream is usually saturated with Oxygen

It’s Carbon-diOxide that fluctuates according to how I breathe.

Skip this if calculations and fine details make you dizzy

Intentionally increasing breathing rate – Fast breathing

As I intentionally increase my breathing rate, Oxygen in my bloodstream stays more or less the same, close to saturation. But, at the same time, extra Carbon-diOxide is expelled from my bloodstream, and its level decreases.

Intentionally decreasing breathing rate – Slow breathing

As I intentionally decrease my breathing rate, my Oxygen level slightly decreases. At the same time, the Carbon-diOxide level in my bloodstream gradually increases, causing a change in the balance between Oxygen and Carbon-diOxide.

Higher levels of Carbon-diOxide, weaken the bond between Oxygen and its hemoglobin carrier, allowing better delivery of Oxygen to my cells. Furthermore, a high level of Carbon-diOxide in my bloodstream dilates my blood vessels allowing better Oxygen delivery.

The advantages of slow breathing:

  • Better absorption of Oxygen in my lungs.
  • Increased availability of Oxygen to my cells.
  • More efficient air filtering.
  • Less muscle power usage.
  • Better recycling of heat and moisture in my nasal cavity.
  • Increased accumulation of Nitric-Oxide in my nasal cavity.

Unfortunately, many tend to breathe fast even when it’s not necessary. Fast breathing, when unnecessary, may deny the advantages mentioned above. So when it comes to breathing, in most cases, “Less is more.”

Some Yogis claim we are given a limited number of breaths right after birth, not a limited amount of time. One may conclude from this claim that those who breathe slowly may live longer. Generally, I’m cautious about longevity advice; however, looking at animals in the wild, those breathing slowly tend to have a longer lifespan.

For example:


Average breaths per minute at rest

Max. lifespan in years (rounded)

Giant turtles









It’s known that many people tend to overeat (in particular in developed countries); similarly, people tend to over-breathe. But, by doing that, they may miss the advantages of slow breathing.

Breathing volume

My breathing may be deep, as a good portion of my lungs inflates, or shallow, as my lungs inflate partially. The amount of air I inhale in every breathing cycle is my breathing volume.

It’s my ‘breathing app’ that controls my unconscious breathing volumes. In one breathing cycle at rest, I inhale a typical air volume. It’s known as “tidal breathing volume.” A healthy person’s tidal breathing volume at rest is about 0.5L (0.13gal), but it can change from moment to moment to be slightly lower or higher than this.

Breathing system volumes

Reserve inhale

The volume of air I can add beyond my tidal breathing to reach a full inhale is my ‘reserve inhale.’ Here is an example that illustrates how to measure reserve inhale volume. Suppose I’m sitting upright, reading a newspaper, and suddenly someone tells me INHALE FULLY! The amount of extra air I can draw is my reserve inhale.

Reserve exhale

The volume of air I can blow beyond my tidal breathing to reach a full exhale is my ‘reserve exhale.’ Here is an example that illustrates how to measure reserve exhale volume. Suppose I’m sitting upright, reading a newspaper, and suddenly someone tells me EXHALE DEEPLY! The amount of extra air I can expel is my reserve exhale.

When I engage in strenuous physical activity, and my muscles require extra energy, I must provide extra air to my lungs. The two reserve volumes allow my lungs to fill with extra needed air. As a result, using these reserves improves my physical performance.

Residual volume

The air that stays at the bottom of my lungs after a deep and full exhale is my ‘residual volume.’ This air volume allows my lungs to exchange gasses after I exhale fully (between breaths). It improves my breathing efficiency.

After a complete exhale, the air left at the bottom of the lungs functions like a flywheel in an inner-combustion engine. The heavy rotating flywheel reduces pulsating and maintains a smooth cyclical rotation between combustion intervals. A car would advance in pulses if there was no flywheel in the car’s motor. Likewise, the residual volume facilitates more continuous Oxygen absorption in the lungs.

Dead space

The cavities of my mouth and nose and all the pipes leading down to the gas exchange areas in my lungs are my ‘dead space.’ These cavities are small in volume. They fill with air when I inhale and stay there until my next exhale. This air doesn’t get exposed to the exchange bubbles. So when taking shallow breaths (inhaling small volumes of air into my lungs), I move air back and forth in my ‘dead space.’

Important: Air in the ‘dead space’ doesn’t participate in the gas exchange process.

Understanding ‘dead space’ helps clarify how some breathing exercises and tools affect me.

Breathing volumes

Skip this if calculations and fine details make you dizzy

On a conscious, forced, and reasonably full inhale, I can add 2.5L (0.6gal) of air on top of the 0.5L (0.13gal) tidal breathing volume I usually inhale at rest. Likewise, on a conscious, forced, and reasonably full exhale, I can empty 1.5L (0.4gal) of air in addition to the 0.5L (0.13gal) tidal breathing volume I normally exhale at rest. This extra inhaling and exhaling capacity is a reserve I use when I need an additional Oxygen supply.

About 1.5L (0.4gal) of air is always stuck at the bottom of my lungs and is difficult to exhale.

Respiratory capacity includes:

  • 5L (0.13gal) tidal volume.
  • 5L (0.6gal) inhale reserve.
  • 5L (0.4gal) exhale reserve.
  • 5L (0.4gal) residual volume (bottom of the lungs).
  • 15L (0.04gal) ‘dead space’ (pipes and cavities).

The total capacity of my lungs is about 6L (1.5gal).

Minute ventilation

My minute ventilation is the combined value of the speed and volume of my breathing. It’s the amount of air I inhale (or exhale) in one minute.

My ‘breathing app’ regulates my minute ventilation by slow, fast, deep, or shallow breathing. I can also intentionally change my minute ventilation.

There is a trade-off between breathing speed and volume. I can maintain the same minute ventilation when I increase the speed and decrease the volume accordingly.

For example, I can inhale a certain amount of air slowly and deeply in one minute. I can also inhale the same amount of air in one minute with fast and shallow breathing.

Skip this if calculations and fine details make you dizzy

Breathing volume X breathing speed = minute ventilation

Average minute ventilation at rest calculation:

0.5L (0.13gal) tidal volume X 14 breaths per minute =

7L (1.7gal) per minute.

Breathing ratios

The duration of my inhaling time compared to my exhaling time defines my breathing ratio. The difference between inhaling and exhaling duration in a single breathing cycle is significant because it affects my heartbeat.

As mentioned, while I inhale, my heart tends to beat slightly faster to support the efforts of my breathing muscles. On the other hand, while I exhale as my breathing muscles effortlessly recoil, my heartbeat slows down.

So in a single breathing cycle, if the inhale duration is longer than the exhale, my heartbeat increases (on average). Conversely, if the exhale duration is longer than the inhale, my heartbeat decreases (on average).

When I’m at rest, my unconscious exhaling duration is typically longer than my unconscious inhaling. But, when I consciously take control of my breathing, I can choose how much time I use for inhaling and exhaling. For example, I can intentionally extend my exhale duration compared to my inhale to decrease my heart rate. Then as my heart rate decreases, my blood pressure follows and goes down. The same is true vice-versa. I can intentionally extend my inhale duration so that my heart rate increases and my blood pressure goes up.

A common method to measure heart rate is to press the fingers on the wrist or behind the earlobes to sense the pulse and then use a stopwatch to count the number of beats in one minute. Some sensitive people claim that while pressing their fingers, they can feel their heart beating faster as they inhale and slowing down as they exhale. That may be true, but I couldn’t replicate it myself.

Relaxing and stimulating effects

As I inhale, unconsciously drawing air into my lungs, my ‘breathing app’ automatically switches on a stimulation response. Likewise, as I exhale and effortlessly expel air out of my lungs, my ‘breathing app’ triggers a relaxation response.

I can do this intentionally. When I intentionally extend the inhale duration, I get stimulated. Conversely, when I intentionally extend the exhale duration, I get relaxed. I can better feel these effects if I keep breathing consistently and rhythmically for a few breathing cycles.

Long ago, people knew the relaxing effects of extending the exhale duration and used it in many spiritual practices. For instance, in some religions, prayers were often said in one long exhale, followed by a short inhale.

So, understanding how breathing duration ratios can relax or stimulate me helps clarify how some breathing exercises and tools affect me.