Authoritative definitions of the International System of Units and SI prefixes.
Dedicated unit pair
Gray to Milligray
Convert Gy to mGy instantly, then review the formula, assumptions, and rounding guidance.
Radiation unitsInstant result
Decimals
Formula result = input × 1 ÷ 0.001. 1 Gy = 1,000 mGy
Common examples
One value, several units
Milligray1,000 mGy
Rad100 rad
Joules per kilogram1 J/kg
Conversion table
| Gy | mGy |
|---|---|
| 1 Gy | 1,000 mGy |
| 2 Gy | 2,000 mGy |
| 5 Gy | 5,000 mGy |
| 10 Gy | 10,000 mGy |
| 25 Gy | 25,000 mGy |
| 50 Gy | 50,000 mGy |
| 100 Gy | 100,000 mGy |
Conversion chart
1 Gy1,000 mGy
5 Gy5,000 mGy
10 Gy10,000 mGy
25 Gy25,000 mGy
50 Gy50,000 mGy
Worked example
1 gray equals 100 rad.
Unit definition
Gray (Gy) One gray equals 1 gray.
Unit history
Gray is represented here using its modern SI definition or an internationally accepted relationship to an SI base unit.
Step by step
1. Parse the value, including fractions.
2. Convert Gy to gray.
3. Convert the base value to mGy and apply your display precision.
Understand the result before using it
Gray to Milligray converts a value measured in Gray (Gy) into the equivalent value in Milligray (mGy). The numerical value changes because the size and definition of the selected unit changes; the underlying quantity does not.
Calculated result
The conversion follows the displayed unit relationship. Display rounding can hide additional digits, and measured inputs cannot become more accurate merely by changing units.
Formula, assumptions, and example
Formula
result = input × 1 ÷ 0.001
Assumptions
- Gray and Milligray represent the same absorbed dose quantity.
- The input is expressed in Gy; the output is expressed in mGy.
- The unit definitions and conventional relationship shown on this page apply.
Worked example
1 Gy = 1,000 mGy. For another value, apply the same relationship and round only to the precision your source measurement supports.
When to use it
Good uses
- Read a Gy measurement in a document that expects mGy.
- Compare a gray value with a value reported in milligray.
- Check the Gy-to-mGy arithmetic before copying the result into another calculation.
Limitations
Common mistakes to avoid
- Absorbed dose, equivalent dose, and activity describe different radiation quantities and are not interchangeable.
- Round the output to a precision justified by the original measurement.
- Verify safety-critical, regulated, laboratory, and contractual conversions against the controlling standard.
Sources and further reading
These references explain the underlying standards or provide authoritative context. Your own contract, institution, clinician, product documentation, local code, or governing standard may be the controlling source.
Guidance on unit names, symbols, conversions, and numerical presentation.
Questions about this calculation
How do I convert Gray to Milligray?
result = input × 1 ÷ 0.001 Using the displayed relationship, 1 Gy equals 1,000 mGy.
How many Milligray are in one Gray?
One Gray is 1,000 Milligray. The displayed digits may be rounded.
Can I reverse the Gy to mGy conversion?
Yes. Swap the source and target units in the converter. The reverse relationship converts mGy back to Gy.
Is the Gray to Milligray result exact?
The conversion follows the displayed unit relationship. Display rounding can hide additional digits, and measured inputs cannot become more accurate merely by changing units.