Education
Everyday radiation dose comparison
Compare rounded teaching numbers side by side. Doses are shown in millisieverts (mSv) and millirem (mrem) using the exact conversion 1 mSv = 100 mrem. This page does not estimate your personal risk or substitute for medical records or professional radiation monitoring.
Choose examples to compare
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Comparison table
| Source | mSv | mrem | Category | Plain-language band |
|---|---|---|---|---|
| Average annual U.S. background radiation (total effective dose, rounded)Typical round-number estimate combining cosmic rays, rocks and soil, small internal contributions, and an average-style radon component. Your location and home ventilation change the parts—not necessarily the same total. | ~3.1 | ~310 | Natural background (annual total) | Moderate (for comparison only) |
| Chest X-ray (single exam, typical adult order-of-magnitude)Technique, equipment, patient size, and number of images strongly change the dose. Ask the imaging facility how they estimate dose for your protocol. | ~0.050 | ~5.00 | Medical diagnostic (single) | Very low |
| CT scan of head (one exam without contrast, rough order)Still far above a single chest film for many protocols, but generally lower than many abdomen/pelvis exams—compare apples to apples with your ordering clinician. | ~1.5 | ~150 | Medical diagnostic (single) | Moderate (for comparison only) |
| Cross-country flight (one way, passenger, rough order)Cosmic-ray dose rate increases with altitude and flight path; crew members accumulate more hours at altitude than occasional travelers. | ~0.050 | ~5.00 | Travel (single trip) | Very low |
| Living near a nuclear power plant (extra public dose above background, illustrative maximum order)Regulated plant emissions are designed to be a small fraction of natural background; site-specific environmental monitoring—not this chart—describes a given community. | ~0.010 | ~1.00 | Public environment (annual extra) | Very low |
Relative dose (log-scaled bars)
Bar length uses a logarithmic stretch so small public doses and larger diagnostic examples fit on one chart. Read exact values in the table—length is for intuition only.
Average annual U.S. background radiation (total effective dose, rounded)
~3.1 mSv (~310 mrem)
CT scan of head (one exam without contrast, rough order)
~1.5 mSv (~150 mrem)
Chest X-ray (single exam, typical adult order-of-magnitude)
~0.050 mSv (~5.00 mrem)
Cross-country flight (one way, passenger, rough order)
~0.050 mSv (~5.00 mrem)
Living near a nuclear power plant (extra public dose above background, illustrative maximum order)
~0.010 mSv (~1.00 mrem)
How to read the bands
Each selected example is placed in one of four comparison bands based only on its millisievert value on this page. Bands describe size for teaching, not prognosis. They do not incorporate your age, health history, or exact exam protocol.
Average annual U.S. background radiation (total effective dose, rounded)
Moderate (for comparison only)
This value describes a whole calendar year of unavoidable background added together. It is not the same kind of event as one CT scan in a single day. Large enough that medical examples at this level are routinely discussed in terms of justification and optimization. It does not, by itself, tell you whether an exam was appropriate for you.
Chest X-ray (single exam, typical adult order-of-magnitude)
Very low
On this comparison chart, this example sits near the bottom. These rounded teaching values are not personal dosimetry and do not predict cancer or other illness for any individual.
CT scan of head (one exam without contrast, rough order)
Moderate (for comparison only)
Large enough that medical examples at this level are routinely discussed in terms of justification and optimization. It does not, by itself, tell you whether an exam was appropriate for you.
Cross-country flight (one way, passenger, rough order)
Very low
On this comparison chart, this example sits near the bottom. These rounded teaching values are not personal dosimetry and do not predict cancer or other illness for any individual.
Living near a nuclear power plant (extra public dose above background, illustrative maximum order)
Very low
On this comparison chart, this example sits near the bottom. These rounded teaching values are not personal dosimetry and do not predict cancer or other illness for any individual.