How Much Radiation?
Scroll up the dose scale — from a banana to a lethal dose — and feel how big (and how small) a sievert really is.
≈ 0.5 bananas
0× a year of natural background
Sleeping next to someone
Spending a night beside another person exposes you to about 0.05 µSv — your own body is faintly radioactive too, thanks to the potassium-40 in your cells. This is roughly half a banana.
≈ 0.5 bananas
Eating a banana
A single banana gives you about 0.1 µSv from its radioactive potassium-40. It's so harmless it became the unofficial unit of radiation: the 'banana equivalent dose'. Everything above is measured in bananas.
≈ 1 bananas
X-ray of an arm
An X-ray of an arm or hand is around 1 µSv — about 10 bananas. The image of your bones costs you less radiation than a couple of cross-country flights' worth of snacks.
≈ 10 bananas
Dental X-ray
A dental X-ray is about 5 µSv, or roughly 50 bananas. Modern dental imaging is among the lowest-dose scans you'll ever get.
≈ 50 bananas
A day of natural background
Just by existing on Earth you absorb about 10 µSv every day — from cosmic rays, rocks, and the air. That's around 100 bananas a day that you can't avoid, and it's completely normal.
≈ 100 bananas
Flight across the US
Flying coast to coast adds about 40 µSv from cosmic rays at altitude — roughly 400 bananas. Frequent flyers and aircrew get more, but it's still trivial.
≈ 400 bananas
Chest X-ray
A chest X-ray is about 0.1 mSv — and here's the famous one: that's about 1,000 bananas. Your body already contains radioactive potassium-40, so you're a walking banana too.
≈ 1,000 bananas
Mammogram
A mammogram delivers about 0.4 mSv, roughly 4,000 bananas. The information it gives doctors vastly outweighs the tiny dose.
≈ 4,000 bananas
A year of natural background
Over a whole year, natural background radiation adds up to about 3 mSv — some 30,000 bananas. This is the baseline everyone on Earth lives with, year after year, harmlessly.
≈ 30,000 bananas
Chest CT scan
A chest CT scan is around 7 mSv — about 70,000 bananas, or more than two years of natural background in a few minutes. Still well below any level linked to measurable harm.
≈ 70,000 bananas
Yearly limit for radiation workers
Regulations cap a radiation worker's dose at 50 mSv per year — about 500,000 bananas. It's set far below the level where harm becomes detectable, with a wide safety margin.
≈ 500,000 bananas
Lowest dose linked to cancer
Around 100 mSv in a single year is the lowest dose clearly linked to a measurable rise in cancer risk. Below this, any effect is too small to detect — which is why everyday doses don't worry scientists.
≈ 1,000,000 bananas
Severe radiation sickness
A dose of about 2 Sv in a short time causes severe radiation sickness — nausea, hair loss, a damaged immune system. With medical care most people survive, but this is where radiation turns dangerous.
≈ 20,000,000 bananas
Often-fatal dose
Around 4 Sv is the LD50/30: without treatment, about half of people die within 30 days. This is roughly 40 million bananas' worth — but delivered all at once, which is what makes it deadly.
≈ 40,000,000 bananas
Chernobyl emergency workers
Some emergency workers at Chernobyl in 1986 received around 6 Sv or more in their effort to contain the disaster. Many did not survive. Their sacrifice helped prevent a far worse catastrophe.
≈ 60,000,000 bananas
Seconds beside an exposed core
Standing next to the exposed Chernobyl reactor core could deliver around 50 Sv in seconds — fatal almost instantly. This is the extreme end of the scale, a world away from the bananas where we started.
≈ 500,000,000 bananas
You reached the dose beside an exposed reactor core — fatal almost instantly.
Radiation is invisible, so our fear of it has no scale. The sievert (Sv) fixes that — but the numbers span nine orders of magnitude, from a banana to a reactor core. The trick to feeling them is the banana: bananas contain radioactive potassium, so eating one gives you about 0.1 µSv. Measure everything in bananas and a chest X-ray becomes 1,000 bananas, a year of natural background 30,000. Scroll up the scale and watch the dose climb — and notice how almost everything everyday is utterly trivial. Danger only begins at the very top.
For information and perspective only — not medical advice. Doses are approximate representative values.
Sources: doses are representative figures from xkcd's radiation chart (Randall Munroe), the US EPA, ICRP, IAEA and NRC, plus standard medical-imaging values. All are approximate. The banana-equivalent dose (1 banana ≈ 0.1 µSv) is an informal but widely used yardstick.
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