How many neutrinos pass through your body every second?

Even when you are reading this sentence, about a hundred trillion neutrinos are passing through your body every second. They travel in straight lines, ignore the matter you are made of almost completely, and leave again on the other side without a trace. The number sounds startling, and the explanation is one of the cleanest ways into what a neutrino actually is.

Where the number comes from

The dominant source is the Sun. Fusion reactions in the solar core produce a steady stream of electron neutrinos that take about eight minutes to reach Earth. Standard solar models predict a total flux at Earth’s surface of roughly 65 billion neutrinos per square centimetre per second — that is, 6.5 × 10¹⁰ neutrinos cross every square centimetre of every surface every second, all day, every day. This figure has been measured directly by experiments such as SNO and Super-Kamiokande and agrees with the predictions of the standard solar model.

To get the number passing through you, multiply the flux by your cross-section — the area of your silhouette. An adult body has a surface roughly the size of a square metre, or about 10,000 square centimetres. Multiplying:

65 billion × 10,000 ≈ 6.5 × 10¹⁴ ≈ 650 trillion solar neutrinos per second

Different popular sources round this to “100 trillion” or “65 trillion” depending on how generously they measure a person, but the order of magnitude is settled: somewhere between roughly 10¹⁴ and 10¹⁵ solar neutrinos pass through your body every second. They reach you continuously.

Why you don’t notice

Neutrinos are very nearly the most retiring particles known. They carry no electric charge, so they ignore the electromagnetic force that governs almost all the chemistry, biology, and sensation in your body. They have almost no mass, so they barely feel gravity. They interact with matter only through the weak nuclear force, which lives up to its name: at the energies of solar neutrinos, the chance of a single neutrino bumping into anything as it crosses your body is around 10⁻²¹ per centimetre of tissue.

Multiply that incredibly small probability by the very large number of neutrinos passing through you, and the arithmetic still favours your body remaining undisturbed. Over an entire human lifetime — roughly 10²³ neutrinos pass through you — only a small handful are expected to scatter inside your tissue at all. The full reasoning is laid out in our explainer on why neutrinos are so hard to detect.

Where the rest of the neutrinos come from

The solar contribution dwarfs everything else, but other neutrino sources do exist:

• Atmospheric neutrinos are produced when cosmic rays hit the upper atmosphere. The flux is on the order of one neutrino per square centimetre per second — minuscule compared with the Sun. See the atmospheric neutrino flux.
• Geo-neutrinos come from the decay of radioactive uranium, thorium, and potassium inside the Earth. They are billions of times rarer than solar neutrinos, but they carry interesting information about the heat budget of the planet. See geo-neutrinos.
• Reactor antineutrinos from nuclear power plants and accelerator neutrinos from particle physics facilities are intense locally but vanishingly small a few hundred kilometres away.
• The cosmic neutrino background is the most numerous of all by density — about 336 relic neutrinos per cubic centimetre, left over from the Big Bang — but at a few ten-thousandths of an electronvolt each, no experiment has yet detected them directly. See the relic neutrino background.
• A nearby galactic supernova would briefly outshine the Sun in neutrinos. The 1987A event in the Large Magellanic Cloud produced about 10¹⁴ neutrinos per square centimetre at Earth in a 13-second burst. See SN 1987A.

For ordinary, everyday counting, none of these come close to the solar flux. The Sun is, by a very wide margin, your personal neutrino source.

Do they still go through you at night?

Yes — and this is one of the more counter-intuitive consequences of how weakly neutrinos interact. The Earth, which is opaque to nearly every other kind of particle, is essentially transparent to neutrinos. When the Sun is below the horizon, its neutrinos pass straight through the planet and reach you from below. The flux through your body at night is almost identical to the flux during the day. Only a tiny fraction get absorbed on the way through; the rest emerge from the far side of the Earth unimpeded.

A useful gut check

If 100 trillion neutrinos cross you every second and almost none of them ever do anything, what makes them worth caring about at all? The answer is that the very rarity of their interactions is exactly what makes them useful as messengers. Because they almost never scatter, they reach us from places no other particle can — the cores of stars, the cores of supernovae, the inside of the Earth. The price of that messenger service is the engineering challenge of detecting them in the first place, which is why neutrino observatories tend to be enormous tanks of water or kilometres-cubed of polar ice.

Want to see the flux interactively? Our Neutrinos-Through-You visualizer shows how the count scales with body size and how trivially small the interaction rate is compared with the flux.

The takeaway

Roughly 10¹⁴ neutrinos pass through your body every second, almost all of them from the Sun. They do so harmlessly because the weak nuclear force is just that — weak. The same property that makes them an enormous experimental challenge also makes them a useful, undisturbed messenger from the universe’s most hidden places.

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Related reading: What is a neutrino?, Why are neutrinos so hard to detect?, How do neutrinos interact with matter?, and Can neutrinos heal cancer? (myth).

Neutrino Times Editorial Team. (2026, May 21). How many neutrinos pass through your body every second?. Neutrino Times. https://neutrino-times.com/articles/how-many-neutrinos-pass-through-you/

Neutrino Times Editorial Team. "How many neutrinos pass through your body every second?." Neutrino Times, May 21, 2026. https://neutrino-times.com/articles/how-many-neutrinos-pass-through-you/.

Neutrino Times Editorial Team. "How many neutrinos pass through your body every second?." Neutrino Times, 21 May. 2026, https://neutrino-times.com/articles/how-many-neutrinos-pass-through-you/.

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