Yoctosievert is 1e-24 sievert units.
Yoctosieverts to Millisieverts Converter — ySv to mSv
Convert Yoctosievert (ySv) to Millisievert (mSv) using the exact conversion factor (1 yoctosievert = 1e-21 millisievert). See the formula, worked examples, and conversion table.
Yoctosieverts to Millisieverts converter
Converter
Radiation Converter
Convert radioactivity, absorbed dose, and equivalent dose units by compatible radiation family.
Context values
Some unit families need one extra value for a physically accurate result.
Millisievert is 0.001 sievert units.
Result = input x 1e-24 / 0.001.
Equivalent Dose units are compatible.
Reserved above the conversion cards and below the converter.
About Converting Yoctosieverts to Millisieverts
Yoctosievert and Millisievert both belong to the radiation-measurement family, though radiation quantities fall into genuinely distinct categories: absorbed dose (gray, rad) measures energy deposited in matter, equivalent dose (sievert, rem) weights that for biological harm, and activity (becquerel, curie) measures how often a radioactive source decays — this page only converts between units of the same kind. Specifically: Yoctosievert is 1e-24 sievert units, and millisievert is 0.001 sievert units.
Formula
millisieverts = yoctosieverts × 1e-21
This factor comes from each unit's defined relationship to the category's base unit: 1 yoctosievert equals 1e-24 base units, and 1 millisievert equals 0.001 base units, so dividing one by the other gives the direct yoctosievert-to-millisievert factor of 1e-21.
Simple example
1 ySv × 1e-21 = 1e-21 mSv
1 yoctosievert = 1e-21 millisieverts.
Real-world example
10 ySv × 1e-21 = 1e-20 mSv
10 yoctosieverts = 1e-20 millisieverts.
Conversion table
| Yoctosievert (ySv) | Millisievert (mSv) |
|---|---|
| 0.001 ySv | 1e-24 mSv |
| 0.01 ySv | 1e-23 mSv |
| 0.1 ySv | 1e-22 mSv |
| 1 ySv | 1e-21 mSv |
| 10 ySv | 1e-20 mSv |
| 100 ySv | 1e-19 mSv |
Reverse conversion: Millisievert to Yoctosievert
1e-21 mSv × 1e+21 = 1 ySv
1e-21 millisieverts = 1 yoctosievert.
yoctosieverts = millisieverts × 1e+21
For a page dedicated to this direction, see Millisievert to Yoctosievert.
Understanding the Yoctosievert (ySv)
Yoctosievert is 1e-24 sievert units.
Understanding the Millisievert (mSv)
Millisievert is 0.001 sievert units.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many millisieverts are in 1 yoctosievert?
1 yoctosievert equals 1e-21 millisieverts, using the exact defined conversion factor rather than an estimate.
How do I convert yoctosievert to millisievert?
Multiply the yoctosievert value by 1e-21. The converter above does this instantly to whatever precision you set.
How do I convert millisievert back to yoctosievert?
Use the reverse factor: 1 millisievert equals 1e+21 yoctosieverts. You can also use the swap control in the converter above to flip the direction instantly.
What is a yoctosievert?
Yoctosievert (ySv) is a unit of radiation.
What is a millisievert?
Millisievert (mSv) is a unit of radiation.
Is the yoctosievert to millisievert conversion exact?
Yes. Both yoctosievert and millisievert are defined by fixed standards rather than physical artifacts, so the factor of 1e-21 used above is exact to as many digits as you choose to display.
What's the difference between absorbed dose, equivalent dose, and activity?
Absorbed dose (gray, rad) measures the energy radiation deposits in matter. Equivalent dose (sievert, rem) adjusts that figure for how harmful different types of radiation are to biological tissue. Activity (becquerel, curie) measures how often a radioactive source decays, independent of how much dose a person actually receives from it.