Medical imaging is the largest man-made source of radiation for most people. Doses vary by machine, body size and technique; the values here are typical adult effective doses. The benefits of a justified scan usually far outweigh the small risk.
How to use the Medical Radiation Dose Calculator
- Dental X-ray (≈ 0.005 mSv)
- Chest X-ray (≈ 0.1 mSv)
- Mammogram (both breasts) (≈ 0.4 mSv)
- Lumbar spine X-ray (≈ 1.4 mSv)
- CT head (≈ 2 mSv)
- CT chest (≈ 7 mSv)
- CT abdomen and pelvis (≈ 10 mSv)
- CT coronary angiogram (≈ 12 mSv)
- PET-CT (≈ 25 mSv)
- Return transatlantic flight (≈ 0.08 mSv)
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter how many of each exam you have had.
Typical effective doses
| Exam | Dose (mSv) | Background equivalent |
|---|---|---|
| Dental X-ray | 0.005 | 1 days |
| Chest X-ray | 0.1 | 12 days |
| Mammogram (both breasts) | 0.4 | 49 days |
| Lumbar spine X-ray | 1.4 | 170 days |
| CT head | 2 | 243 days |
| CT chest | 7 | 852 days |
| CT abdomen and pelvis | 10 | 1217 days |
| CT coronary angiogram | 12 | 1460 days |
| PET-CT | 25 | 3042 days |
| Return transatlantic flight | 0.08 | 10 days |
Tips
- Keep a record of your imaging and its doses.
- Ask whether an ultrasound or MRI could answer the question without radiation.
- Tell staff if you might be pregnant.
- Background radiation varies by altitude and region.
Common mistakes to avoid
- Comparing mSv (effective dose) with mGy (absorbed dose).
- Assuming every scan of the same type gives the same dose.
- Ignoring cumulative dose from repeated scans.
Inputs explained
| Field | What to enter |
|---|---|
| Dental X-ray (≈ 0.005 mSv) | A number |
| Chest X-ray (≈ 0.1 mSv) | A number |
| Mammogram (both breasts) (≈ 0.4 mSv) | A number |
| Lumbar spine X-ray (≈ 1.4 mSv) | A number |
| CT head (≈ 2 mSv) | A number |
| CT chest (≈ 7 mSv) | A number |
| CT abdomen and pelvis (≈ 10 mSv) | A number |
| CT coronary angiogram (≈ 12 mSv) | A number |
| PET-CT (≈ 25 mSv) | A number |
| Return transatlantic flight (≈ 0.08 mSv) | A number |
What each result means
- Total effective dose = [Dental X-ray (≈ 0.005 mSv)]×0.005 + [Chest X-ray (≈ 0.1 mSv)]×0.1 + [Mammogram (both breasts) (≈ 0.4 mSv)]×0.4 + [Lumbar spine X-ray (≈ 1.4 mSv)]×1.4 + [CT head (≈ 2 mSv)]×2 + [CT chest (≈ 7 mSv)]×7 + [CT abdomen and pelvis (≈ 10 mSv)]×10 + [CT coronary angiogram (≈ 12 mSv)]×12 + [PET-CT (≈ 25 mSv)]×25 + [Return transatlantic flight (≈ 0.08 mSv)]×0.08
- Equivalent days of natural background radiation = [Total effective dose]÷3×365
- Approximate extra lifetime cancer risk = [Total effective dose]×0.005
- Equivalent number of chest X-rays = [Total effective dose]÷0.1
Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.
Formula
Total dose (mSv) = Σ number of exams × typical dose
Days of background radiation = total ÷ 3 mSv × 365
Approximate extra lifetime cancer risk ≈ 5% per sievert (0.005% per mSv)
Worked example
Inputs — Dental X-ray (≈ 0.005 mSv): 0; Chest X-ray (≈ 0.1 mSv): 1; Mammogram (both breasts) (≈ 0.4 mSv): 0; Lumbar spine X-ray (≈ 1.4 mSv): 0; CT head (≈ 2 mSv): 0; CT chest (≈ 7 mSv): 1; CT abdomen and pelvis (≈ 10 mSv): 0; CT coronary angiogram (≈ 12 mSv): 0; PET-CT (≈ 25 mSv): 0; Return transatlantic flight (≈ 0.08 mSv): 0.
Results — Total effective dose = 7.1 mSv; Equivalent days of natural background radiation = 864 days; Approximate extra lifetime cancer risk = 0.0355 %; Equivalent number of chest X-rays = 71.
Key terms
- mSv
- Millisievert, unit of effective dose.
Frequently asked questions
How much radiation is in a CT scan?
Typically 2 mSv for the head and 7–10 mSv for the chest or abdomen.
What is natural background radiation?
About 3 mSv a year on average in the US (2–3 mSv in most places).
Are X-rays dangerous?
The risk from a single scan is very small; avoid unnecessary repeat imaging.