# Medical Radiation Dose Calculator (X-ray and CT)

URL: https://speedycalculator.com/calculators/health/medical-radiation/
Last updated: 2026-10-30

> The medical radiation calculator adds up the typical effective dose from X-rays, CT scans and other imaging you have had, compares it with natural background radiation and estimates the small extra lifetime cancer risk.

## Inputs

- 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

- Total effective dose
- Equivalent days of natural background radiation
- Approximate extra lifetime cancer risk
- Equivalent number of chest X-rays

## 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)
```

## Explanation

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

ExamDose (mSv)Background equivalentDental X-ray0.0051 daysChest X-ray0.112 daysMammogram (both breasts)0.449 daysLumbar spine X-ray1.4170 daysCT head2243 daysCT chest7852 daysCT abdomen and pelvis101217 daysCT coronary angiogram121460 daysPET-CT253042 daysReturn transatlantic flight0.0810 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

FieldWhat to enterDental X-ray (≈ 0.005 mSv)A numberChest X-ray (≈ 0.1 mSv)A numberMammogram (both breasts) (≈ 0.4 mSv)A numberLumbar spine X-ray (≈ 1.4 mSv)A numberCT head (≈ 2 mSv)A numberCT chest (≈ 7 mSv)A numberCT abdomen and pelvis (≈ 10 mSv)A numberCT coronary angiogram (≈ 12 mSv)A numberPET-CT (≈ 25 mSv)A numberReturn 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.*

## 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.

## FAQ

**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.


## Sources

- [RadiologyInfo.org – Radiation dose in X-ray and CT exams](https://www.radiologyinfo.org/en/info/safety-xray)