Convert between Sv, mSv, µSv, rem, mrem, Gy, mGy, rad, and Röntgen. Shows risk level, dose equivalences, and weighting factors.
Radiation dosimetry uses multiple overlapping unit systems — Sieverts and rem for equivalent dose, Grays and rad for absorbed dose, and Röntgen for exposure — that confuse even healthcare professionals. The SI system (Sv, Gy) coexists with the older CGS system (rem, rad) in practice, and converting between them requires understanding the radiation weighting factor (wR) that accounts for biological damage differences between radiation types.
This converter handles nine radiation dose units with automatic cross-conversion, includes a radiation weighting factor input for accurate Gray ↔ Sievert conversion, and provides essential context: risk-level indicators, equivalences in chest X-rays and background radiation years, a reference table of common radiation doses from medical imaging to lethal exposures, and a weighting factor table for different radiation types.
For medical physicists, radiologic technologists, nuclear workers, health physics students, and anyone receiving medical imaging, this tool provides quick, accurate dose unit conversion with the safety context that radiation measurements always need.
Radiation dose involves multiple unit systems (SI vs CGS), multiple dose concepts (absorbed vs equivalent), and critical safety context. This converter handles all of that without requiring you to remember conversion factors or look up weighting tables separately. Keep these notes focused on your operational context. Tie the context to the calculator’s intended domain. Use this clarification to avoid ambiguous interpretation.
Equivalent dose (Sv) = Absorbed dose (Gy) × wR 1 Sv = 100 rem 1 Gy = 100 rad 1 R ≈ 0.00877 Sv (for soft tissue) wR = 1 (X-rays, gamma, beta), 2 (protons), 5–20 (neutrons), 20 (alpha)
Result: 1,000 mrem
10 mSv × 100 mrem/mSv = 1,000 mrem. This is equivalent to a CT abdomen scan — about 500 chest X-rays or 3.2 years of US background radiation.
There are three related but distinct quantities: - **Absorbed dose (Gy/rad)**: Physical energy deposited per kg of tissue. Same for all radiation types. - **Equivalent dose (Sv/rem)**: Absorbed dose × wR. Accounts for biological effectiveness of different radiation types. - **Effective dose (Sv/rem)**: Equivalent dose × tissue weighting factor. Accounts for different organ sensitivities. This is what's usually reported for medical imaging.
| Dose | Effect | |---|---| | < 250 mSv | No observable acute effects | | 500 mSv | Nausea, reduced blood cell count | | 1,000 mSv (1 Sv) | Radiation sickness, recovery likely | | 4,000 mSv (4 Sv) | LD50 — 50% mortality without treatment | | 6,000+ mSv | Fatal within weeks even with treatment |
Radiation protection follows ALARA — As Low As Reasonably Achievable. Every medical imaging decision balances diagnostic benefit against radiation risk. The goal is not zero exposure but justified, optimized exposure.
Gray (Gy) measures absorbed physical dose — energy deposited per kg of tissue. Sievert (Sv) measures equivalent biological dose — Gy multiplied by a weighting factor that accounts for different radiation types damaging DNA differently.
1 Sv = 100 rem. Sievert is SI; rem is the older CGS unit. The US nuclear industry still commonly uses rem/mrem, while international bodies use Sv/mSv.
There is no universally "safe" dose — the Linear No-Threshold (LNT) model assumes any dose carries some risk. The US annual occupational limit is 50 mSv, and the public limit is 1 mSv above background (3.1 mSv/year).
A CT abdomen (~10 mSv) equals about 500 chest X-rays (~0.02 mSv each).
Different radiation types cause different biological damage. Alpha particles (wR = 20) are 20× more biologically damaging per Gray than X-rays (wR = 1) because they deposit energy densely along a short track, causing clustered DNA damage.
A unit of radiation exposure (ionization in air). It is approximately equivalent to 8.77 mSv for soft tissue. Named after Wilhelm Röntgen, who discovered X-rays.