About the Radiation Dose Calculator
This radiation dose calculator adds up your estimated effective dose for a year, in millisieverts (mSv), from medical imaging, air travel and the natural background radiation everyone receives. Enter how many of each scan or X-ray you have had and how many long flights you took, and it totals your dose, breaks it down by source and compares it with the average American’s exposure.
Exam doses are the typical adult values published by RadiologyInfo.org, the patient site of the American College of Radiology and the Radiological Society of North America — for example 0.1 mSv for a chest X-ray, 6.1 mSv for a chest CT and 22.7 mSv for a whole-body PET/CT. Natural background is about 3 mSv a year in the US (about 1.5 mSv more at high altitude), and the CDC estimates about 0.035 mSv for a one-way coast-to-coast flight. The NCRP (Report No. 160, cited by the US EPA) puts the average US total at about 6.2 mSv per person per year. Exam doses are as listed by RadiologyInfo.org in its April 2025 review.
Actual doses vary considerably with body size, the scanner and the protocol used, so treat the result as an order-of-magnitude estimate. The dose from a medically justified scan is almost always far outweighed by the benefit of an accurate diagnosis — never skip an exam your doctor recommends because of this number.
With the default inputs, the estimated yearly dose is 10.96 mSv. Change any value above to recalculate instantly.
How to use the radiation dose calculator
- 1Enter how many of each X-ray or scan you have had in the past year.
- 2Add the number of long flights you took.
- 3Switch on high altitude if you live somewhere like Colorado or New Mexico.
- 4Add any other dose from your imaging records, then read your yearly total.
- 5Compare the total and the breakdown with the US average of 6.2 mSv.
Formula and method
Effective dose, measured in millisieverts, weights the radiation absorbed by each organ by how sensitive that tissue is, so doses from very different exposures — a dental X-ray, a CT scan, a flight — can be added together and compared. The calculator multiplies the number of each exam by its typical adult dose from RadiologyInfo.org, adds 0.035 mSv per long flight (the CDC estimate for a one-way US coast-to-coast trip) and a year of natural background radiation.
Natural background averages about 3 mSv a year in the US, mostly from radon gas in homes, with about 1.5 mSv more at high altitude. Millirem are the older US unit: 1 mSv = 100 mrem. Chest-X-ray equivalents divide the total by 0.1 mSv.
- mSv
- Millisievert, unit of effective dose (1 mSv = 100 mrem)
- 0.035
- mSv per one-way coast-to-coast flight (CDC)
- 3
- mSv per year of US natural background radiation
Worked examples
Chest X-ray, 4 dental X-rays, one abdominal CT and 4 flights
Medical dose is 0.1 + 4 × 0.005 + 7.7 = 7.82 mSv. Four flights add 0.14 mSv and background adds 3 mSv, for a total of 10.96 mSv — about 177% of the US average, mostly from the single CT scan.
Routine year: one mammogram, two dental X-rays, no flights
A mammogram (0.28 mSv) and two dental X-rays (0.01 mSv) add only 0.29 mSv to the 3 mSv background, for 3.29 mSv — about half the US average.
Denver resident with a PET/CT and 20 flights
Background rises to 4.5 mSv at altitude, 20 flights add 0.7 mSv and a whole-body PET/CT adds 22.7 mSv, giving 27.9 mSv — still well below the 50 mSv yearly limit for radiation workers.
Frequently asked questions
How much radiation is a CT scan?+
Typical adult doses are about 1.6 mSv for a head CT, 6.1 mSv for a chest CT, 7.7 mSv for an abdomen and pelvis CT and 8.8 mSv for a spine CT, according to RadiologyInfo.org. A chest CT is roughly equal to two years of natural background radiation.
What is a normal yearly radiation dose?+
The average person in the US receives about 6.2 mSv a year, according to the NCRP: roughly half from natural sources such as radon and cosmic rays and about half from medical procedures, especially CT scans.
How much radiation do you get from flying?+
The CDC estimates about 0.035 mSv for a one-way flight across the US from coast to coast. Two such trips are roughly equal to one chest X-ray. Frequent flyers and aircrew receive noticeably more over a year.
What is the safe limit for radiation exposure?+
There is no sharp safe threshold, but regulatory limits give context: the NRC limits members of the public to 1 mSv a year from licensed sources (excluding background and medical) and radiation workers to 50 mSv a year. Medical imaging has no fixed limit because each exam should be justified by its benefit.
How do I convert mSv to mrem?+
Multiply millisieverts by 100 to get millirem: 1 mSv = 100 mrem, and 6.2 mSv = 620 mrem. Sieverts and rem are the larger units: 1 Sv = 100 rem.
This tool gives general estimates and is not medical advice. Talk to a doctor or qualified professional about your health, diet or training.