Radiation Dose Comparison Calculator
Compare radiation exposure from chest X-ray (0.1 mSv), CT scan (7 mSv), and flights against the 2.4 mSv annual background dose in μSv and mSv.
Radiation dose quantifies how much ionizing radiation energy has been absorbed by biological tissue. The measurement is critical in medical imaging, nuclear safety, cancer radiotherapy, and radiation worker protection.
Key units and formulas:
Absorbed Dose (physical): D (gray, Gy) = Energy Absorbed (joules) ÷ Mass of Tissue (kg) 1 Gy = 1 J/kg
Equivalent Dose (biological effect): H (sievert, Sv) = D (Gy) × Radiation Weighting Factor (Wr)
Weighting factors by radiation type:
| Radiation Type | Wr |
|---|---|
| X-rays, gamma rays, beta | 1 |
| Protons | 2 |
| Alpha particles | 20 |
| Neutrons (fast) | 10–20 |
Effective Dose (accounting for tissue sensitivity): E (Sv) = Σ (H × Tissue Weighting Factor) Different organs have different radiosensitivity: bone marrow = 0.12, lung = 0.12, breast = 0.12, thyroid = 0.04, bone surface = 0.01.
Dose rate: D_rate = Total Dose ÷ Time
Common radiation exposure benchmarks:
| Exposure | Dose |
|---|---|
| Chest X-ray | ~0.1 mSv |
| Dental X-ray (bitewing) | ~0.005 mSv |
| CT scan (chest) | ~7 mSv |
| Mammogram | ~0.4 mSv |
| Annual background radiation (US average) | ~3.1 mSv |
| Transatlantic flight | ~0.08 mSv |
| Annual limit for radiation workers (US) | 50 mSv |
| Acute radiation sickness threshold | ~1,000 mSv (1 Sv) |
| Lethal dose (50% mortality, 30 days) | ~4,000–5,000 mSv |
Worked example: A radiation worker receives 2 mGy of X-rays (Wr = 1) and 0.5 mGy of fast neutrons (Wr = 10).
Equivalent dose = (2 mGy × 1) + (0.5 mGy × 10) = 2 + 5 = 7 mSv
This is well within the 50 mSv annual occupational limit but represents 2.3× the average American’s total annual background exposure.
ALARA principle: In radiation protection, all exposures should be kept As Low As Reasonably Achievable — meaning dose minimization is a continuous goal, not just staying under legal limits.