Radiation Converter — Gray, Rad & Sievert Converter
Convert radiation absorbed dose between different units including gray, rad, milligray, centigray, sievert, and more. Essential for radiation therapy, nuclear safety, and health physics. See also our Radiation Exposure Converter and Energy Converter.
Value:
How to Convert Radiation Dose
- Enter the radiation dose value in the input field above.
- Select the unit you are converting from in the "From" dropdown menu.
- Select the unit you want to convert to in the "To" dropdown menu.
- The result will automatically appear in the result field.
- Use the copy button to copy the result to your clipboard.
- Click any conversion in the list below to quickly select those units.
Radiation Dose Formula
Absorbed Dose Definition:
D = E/m
Where:
D = Absorbed dose (Gy or J/kg)
E = Energy absorbed (J)
m = Mass of material (kg)
Unit Relationships:
1 Gy = 100 rad = 100 cGy
1 Gy = 1 J/kg = 10⁴ erg/g
1 rad = 0.01 Gy = 1 cGy
1 mGy = 0.1 rad = 100 μGy
Equivalent Dose:
H = D × wR (sievert)
Where: wR = radiation weighting factor
For gamma/X-rays: wR = 1 (so 1 Gy = 1 Sv)
For alpha particles: wR = 20
For neutrons: wR = 5-20
Effective Dose:
E = Σ(wT × HT)
Where: wT = tissue weighting factorExample Conversion
Problem: Convert 2 Gy to rad and cGy.
Given: D = 2 Gy
Solution:
• To rad: 2 Gy × 100 rad/Gy = 200 rad
• To cGy: 2 Gy × 100 cGy/Gy = 200 cGy
Answer: 2 Gy = 200 rad = 200 cGy
Technical Details
Radiation absorbed dose measures the energy deposited by ionizing radiation per unit mass of material. The gray (Gy) is the SI unit, while the rad (radiation absorbed dose) is the older CGS unit still used in some contexts. In radiation therapy, doses are typically prescribed in gray or centigray (1 cGy = 1 rad), making the centigray a bridge between old and new systems.
The sievert (Sv) measures equivalent dose, which accounts for the biological effectiveness of different radiation types. For gamma rays and X-rays, 1 Gy = 1 Sv numerically, but for alpha particles, 1 Gy = 20 Sv due to their higher biological damage. Annual occupational dose limits are typically 20-50 mSv, while a single radiation therapy fraction delivers 1.8-2 Gy to the tumor.
Radiation Dose Reference Table
| Exposure | Typical Dose | Context |
|---|---|---|
| Chest X-ray | 0.02 mGy | Diagnostic imaging |
| CT scan (abdomen) | 10-20 mGy | Diagnostic imaging |
| Annual background | 2.4 mSv | Natural radiation exposure |
| Occupational limit | 20 mSv/year | Radiation worker safety |
| Radiation therapy fraction | 1.8-2 Gy | Cancer treatment per session |
| Total therapy course | 50-70 Gy | Full cancer treatment |
| Acute radiation syndrome | 1-6 Gy (whole body) | Emergency exposure |
| Food sterilization | 10-50 kGy | Industrial irradiation |
Frequently Asked Questions
What is the difference between gray and sievert?
Gray (Gy) measures absorbed dose (energy per mass), while sievert (Sv) measures equivalent dose (biological effect). For X-rays and gamma rays, they are numerically equal. For alpha particles, 1 Gy = 20 Sv because alpha radiation causes 20 times more biological damage per unit energy.
How do you convert between gray and rad?
1 gray = 100 rad, or 1 rad = 0.01 Gy = 10 mGy. The centigray (cGy) equals exactly 1 rad, making it convenient for converting between systems. In radiation therapy, prescriptions may use either unit.
What is a safe radiation dose?
Background radiation averages about 2.4 mSv/year. Occupational limits are 20 mSv/year (ICRP) or 50 mSv/year (US NRC). Public limits are 1 mSv/year above background. Acute whole-body doses above 1 Sv cause radiation sickness, and above 6 Sv are typically fatal.
Why is centigray used in radiation therapy?
Centigray (cGy) is numerically equal to rad (1 cGy = 1 rad), providing a convenient bridge between the old CGS system and modern SI units. Many radiation therapy protocols historically used rad, so cGy maintains numerical continuity while using SI-based units.
What radiation weighting factors are used?
Radiation weighting factors (wR) convert absorbed dose to equivalent dose: photons/electrons wR=1, protons wR=2, alpha particles wR=20, neutrons wR=5-20 (energy dependent). These reflect the relative biological effectiveness of different radiation types.
Objective of Measurement:
Measurement is the most important aspect of our life. We use measurement in science, engineering, business trading, personal life, education, and more other fields. As technology is growing day by day so we need a highly accurate and easy convenient global measuring system in each and every field. It is essential to use standard measurement in every field that everyone to be sure that they not get cheated.
History of Measurement:
In history for measurement people used the human body as a tool. For measuring length used forearm, hand, foot & finger as a unit. The foot, finger is a subdivided shorter unit of a length. This type of measurement is not accurate cause different in size of the arm & finger for different people & some of the countries still using it. In history, there were lots of measuring systems developed but mostly used imperial, the metric system of measurement. We use these systems for measure distances, volume, weight, speed, area etc. Due to this a major problem everyone is facing while doing trading between the countries. A huge improvement in civilization, It necessary to improve measuring standards. Nowadays International Standard (SI) units are used as a global measurement system.
Radiation Conversion - Unit Converter:
Our radiation conversion converter convert gray [Gy], milligray [mGy], microgray [μGy], rad [rad], millirad [mrad], kilogray [kGy], centigray [cGy], joule/kilogram [J/kg], millijoule/kilogram [mJ/kg], erg/gram [erg/g], sievert [Sv], millisievert [mSv] vice versa with metric conversion.
Radiation dose conversions & its abbreviations
| Unit | Abbreviation | Unit | Abbreviation |
|---|---|---|---|
| gray | Gy | milligray | mGy |
| microgray | μGy | rad | rad |
| millirad | mrad | kilogray | kGy |
| centigray | cGy | joule/kilogram | J/kg |
| erg/gram | erg/g | sievert | Sv |
| millisievert | mSv | millijoule/kilogram | mJ/kg |
Complete list of Radiation dose conversion units and its conversion.
1 gray [Gy] = 100 rad [rad]
1 rad [rad] = 0.01 gray [Gy]
1 gray [Gy] = 1000 milligray [mGy]
1 milligray [mGy] = 0.001 gray [Gy]
1 gray [Gy] = 100 centigray [cGy]
1 centigray [cGy] = 0.01 gray [Gy]
1 gray [Gy] = 1 sievert [Sv] (for gamma rays)
1 sievert [Sv] = 1000 millisievert [mSv]