About the CT effective dose calculator
This calculator converts a CT scan's dose-length product (DLP) — the total radiation output reported on the scanner's dose page — into an effective dose in millisieverts (mSv), then compares that dose with natural background radiation and a population-level cancer-risk estimate.
How the effective dose is calculated
Effective dose equals the DLP multiplied by a region-specific conversion factor (k), in the form E = k x DLP. The k factor accounts for how radiosensitive the scanned organs are and ranges from about 0.0021 mSv per mGy·cm for a head CT up to about 0.019 for a spine CT (AAPM Report 96 and European CT dosimetry guidance). Multiplying the per-scan dose by the number of scans gives a cumulative effective dose for repeated exams of the same type.
Putting the dose in context
The calculator expresses the total dose as an equivalent number of years of natural background radiation, using either the US average of about 3.1 mSv per year (NCRP Report 160) or the global average of about 2.4 mSv per year (UNSCEAR). It also applies the ICRP Publication 103 nominal risk coefficient of about 5.5% per sievert to estimate an added lifetime cancer risk from a linear no-threshold model. This is a population average, not an individual prediction.
When to consult a professional
This tool performs the standard dose-length-product arithmetic for education and record-keeping; it does not replace the dose report from your imaging center or advice from your referring physician or radiologist. Decisions about additional imaging should weigh the diagnostic benefit against the estimated radiation dose, ideally with a clinician who knows your full history.