Radiation Absorbed Dose Converter
Convert an absorbed radiation dose between grays, milligrays, micrograys, rads, and millirads. Enter a value and choose the units to convert from and to.
Convert Absorbed Radiation Dose Between Units
Radiation Absorbed Dose Formula
Where:
- \(D_{\mathrm{from}}\) — the entered absorbed dose in the selected starting unit
- \(D_{\mathrm{to}}\) — the converted absorbed dose in the selected target unit
- \(f_{\mathrm{from}}\) and \(f_{\mathrm{to}}\) — factors that convert each selected unit to grays (Gy)
The calculator first converts the entered value to grays, then divides by the factor for the target unit. The factors are 1 for Gy, 0.001 for mGy, 0.000001 for µGy, 0.01 for rad, and 0.00001 for mrad.
Radiation Absorbed Dose – Calculation Example
Example: with the default settings, convert an absorbed dose of 1 gray to rads.
\[D_{\mathrm{rad}}=1\,\mathrm{Gy}\times\frac{1}{0.01}=100\,\mathrm{rad}\]
Result: 1 Gy = 100 rad.
How to use the calculator
- Enter a nonnegative number in Absorbed dose value. Use the value as stated in your measurement or source document.
- Choose its current unit under From unit: Gray (Gy), Milligray (mGy), Microgray (µGy), Rad, or Millirad.
- Choose the unit you need under To unit. The Converted Absorbed Dose result displays the converted number and its unit.
You can select the same unit in both menus to leave the numerical value unchanged. Check both selections before copying a result: a milligray and a microgray differ by a factor of 1,000.
What absorbed dose means
Absorbed dose is the energy deposited by ionizing radiation per unit mass of material. Its SI unit, the gray, is defined as one joule of deposited energy per kilogram: \(1\,\mathrm{Gy}=1\,\mathrm{J/kg}\). The rad is an older unit of the same quantity. Converting between grays and rads changes how a dose is expressed, not the physical dose itself.
Absorbed dose is used to describe energy deposited in tissue or other materials, including in radiation therapy, radiation biology, and radiation protection. Its meaning depends on what material or tissue received the dose and where the dose was measured. A converted number does not supply that context.
Absorbed dose is not the same as equivalent or effective dose, which are expressed in sieverts and account for additional radiation-protection factors. Do not convert Gy directly to Sv using this tool: the numerical relationship depends on the radiation type and, for effective dose, the tissues involved. Absorbed dose also differs from the frequency of electromagnetic radiation; a frequency converter changes units of oscillation, not units of deposited energy per mass.
Unit relationships and practical limits
| Unit | Equivalent in grays | Useful relationship |
|---|---|---|
| Gray (Gy) | 1 Gy | 1 Gy = 1 J/kg = 100 rad |
| Milligray (mGy) | 0.001 Gy | 1 mGy = 1,000 µGy |
| Microgray (µGy) | 0.000001 Gy | 1 µGy = 0.1 mrad |
| Rad | 0.01 Gy | 1 rad = 10 mGy |
| Millirad (mrad) | 0.00001 Gy | 1 mrad = 10 µGy |
Joules per kilogram defines the gray, but J/kg is not a selectable unit in this calculator. If a source gives absorbed dose in J/kg, its numerical value is the same in Gy. The calculator accepts nonnegative values; a negative absorbed dose is not a meaningful input here.
The result is a unit conversion, not a measurement or an assessment of risk. It cannot determine how a dose was distributed through an object, which radiation produced it, or whether a reported value is appropriate for a particular application. Keep the significant figures justified by your original data; conversion does not make a measurement more precise. Very small converted values may display as zero because the calculator rounds its output.
Do not confuse absorbed dose with a rate or a flux. Dose rate needs a time unit, such as Gy per hour, while heat flux density describes energy transfer per area per time. Neither is directly interchangeable with an absorbed dose in Gy without additional information.
Frequently Asked Questions
How do I convert rads to micrograys by hand?
Multiply the number of rads by 10,000. One rad equals 0.01 gray, and one gray equals 1,000,000 micrograys, so 0.01 gray equals 10,000 micrograys. For example, 0.2 rad is 2,000 micrograys. To reverse the conversion, divide the microgray value by 10,000.
What is a normal or safe absorbed dose?
There is no single normal or safe absorbed dose for every situation. The significance of a value depends on which tissue received it, how much tissue was exposed, and whether the dose was delivered at once or over time. A dose used intentionally in radiation therapy should not be compared directly with a diagnostic imaging dose. Ask a qualified clinician or radiation-safety professional to interpret an individual exposure.
Can I convert grays to becquerels?
No. Grays measure energy deposited per kilogram of material, while becquerels measure the number of radioactive decays per second. Activity alone does not tell you how much radiation reaches or is absorbed by a person or object. Estimating dose from activity requires more information, including the radionuclide, its location, exposure duration, and the path radiation takes through material.
Can I add absorbed doses from separate exposures?
You can add absorbed doses when they refer to the same material or tissue and a clearly defined measurement point or region. First express the values in the same unit. Adding a dose to one organ to a dose to another does not produce a meaningful single-organ absorbed dose. For health-risk assessment, the distribution of exposure and other factors also matter.
How do I calculate absorbed dose from a dose rate?
Multiply a constant absorbed-dose rate by the time spent exposed, using compatible time units. For example, 2 milligrays per hour for 30 minutes gives 1 milligray. If the rate varies, the total dose depends on how it changes over the exposure period; multiplying by a single reading may be misleading. This converter changes dose units but does not perform that time calculation.
Can I convert roentgens to grays or rads?
Not with a universal conversion factor. The roentgen is a unit of radiation exposure in air, whereas the gray and rad measure energy absorbed per unit mass. The absorbed dose associated with a roentgen reading depends on factors such as photon energy and the material receiving the radiation. Do not treat a roentgen value as a rad value without an appropriate, documented conversion.