BREATHS
0 since the page openedResting rate: 15 a minute. The actual rate varies with activity and health.
WHILE YOU READ THIS
0
heartbeats since you opened this page.
The counter estimates heartbeats using a resting pulse of 72 a minute. Below, explore other bodily rhythms.
01Right now
These numbers increase at the average rates chosen for this calculation. They are not measurements of your body.
RED BLOOD CELLS MADE
0 made by marrowMarrow makes 2.4 million a second, day and night. Nearly nine in ten cells produced each day are blood cells.
SKIN CELLS SHED
0 released into the world5,800 a second. Part of the dust on your shelves is, literally, you.
BLOOD PUMPED
0 litres5 litres a minute, at rest. A volume the size of an Olympic pool passes through your heart in about a year.
HAIR GROWN
0 nanometres, on your headYour scalp adds 0.35 mm a day. This is an approximate growth rate for one hair.
BLINKS
0 since the page opened15 a minute. Each one cuts the picture of the world for a third of a second.
02A lifetime
Choose an age to estimate the totals, assuming the same average rates every year.
- Heartbeats
- 0
- Breaths
- 0
- Blood pumped
- 0Olympic pools
- Epidermal turnovers
- 0about one every 47 days
- Bone-remodelling cycles
- 0full cycles
- Eyes shut
- 0years, from blinking alone
- Dreaming
- 0years of REM sleep
Assumptions, at rest: 72 beats a minute, 15 breaths a minute, 5 litres of blood a minute; blinking: 15 a minute, a third of a second each, 16 hours awake a day; dreaming: 100 minutes a night. Actual rates vary between people and over a lifetime.
03The billion-beat club
In many mammals, resting pulse and lifespan roughly compensate for each other: the result is on the order of a billion beats. A mouse reaches it in two years, an elephant in seventy. Humans are a clear exception: about three billion.
billions of beats per lifetime · rough estimate: average pulse × average lifespan
04What changes slowly
Renewal has limits. Four tissues run on a different clock:
- THE CORTEX
Many of the cortical neurons you are using to read this sentence are the same ones you had twenty years ago. They renew very slowly.
- THE LENS
The core of the lens through which you see this screen formed before birth. Its proteins are not renewed.
- THE OOCYTES
The ovarian reserve forms before birth and declines afterwards. No postnatal production has been demonstrated clinically.
- HEART MUSCLE
It renews by about 1% a year at age 25 and 0.45% at age 75. Over a normal lifespan, fewer than half of the cardiomyocytes are exchanged.
The egg you came from formed inside your mother's ovary, while she was still a foetus. The cell began forming before she was born.