Femtogray is 1e-15 gray units.
Femtograys to Rads Converter — fGy to rad
Convert Femtogray (fGy) to Rad (rad) using the exact conversion factor (1 femtogray = 1e-13 rad). See the formula, worked examples, conversion table, and common uses.
Femtograys to Rads 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.
Rad is 0.01 gray.
Result = input x 1e-15 / 0.01.
Absorbed Dose units are compatible.
Reserved above the conversion cards and below the converter.
About Converting Femtograys to Rads
Femtogray and Rad 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: Femtogray is 1e-15 gray units, and rad is 0.01 gray.
Formula
rads = femtograys × 1e-13
This factor comes from each unit's defined relationship to the category's base unit: 1 femtogray equals 1e-15 base units, and 1 rad equals 0.01 base units, so dividing one by the other gives the direct femtogray-to-rad factor of 1e-13.
Simple example
1 fGy × 1e-13 = 1e-13 rad
1 femtogray = 1e-13 rads.
Real-world example
10 fGy × 1e-13 = 1e-12 rad
10 femtograys = 1e-12 rads.
Conversion table
| Femtogray (fGy) | Rad (rad) |
|---|---|
| 0.001 fGy | 1e-16 rad |
| 0.01 fGy | 1e-15 rad |
| 0.1 fGy | 1e-14 rad |
| 1 fGy | 1e-13 rad |
| 10 fGy | 1e-12 rad |
| 100 fGy | 1e-11 rad |
Reverse conversion: Rad to Femtogray
1e-13 rad × 1e+13 = 1 fGy
1e-13 rads = 1 femtogray.
femtograys = rads × 1e+13
For a page dedicated to this direction, see Rad to Femtogray.
Understanding the Femtogray (fGy)
Femtogray is 1e-15 gray units.
Understanding the Rad
Rad (rad) measures absorbed radiation dose. 'Radiation absorbed dose' — the US customary unit of absorbed radiation dose, fixed at exactly 0.01 gray. It is classified as a non-SI unit, still common in the US.
Where it's used: Still used in some US medical and historical contexts alongside the SI gray
Rad vs. gray. Both measure absorbed radiation dose; the gray is the modern SI unit while the rad is the older US customary unit, related by 1 gray = 100 rad exactly.
Uses of the Rad today
- US radiation therapy dose records (historically)
- US nuclear regulatory and medical physics contexts
Rad — sources
- NIST Guide to the SI, Appendix B — Lists the rad among non-SI units with an exact SI equivalence.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many rads are in 1 femtogray?
1 femtogray equals 1e-13 rads, using the exact defined conversion factor rather than an estimate.
How do I convert femtogray to rad?
Multiply the femtogray value by 1e-13. The converter above does this instantly to whatever precision you set.
How do I convert rad back to femtogray?
Use the reverse factor: 1 rad equals 1e+13 femtograys. You can also use the swap control in the converter above to flip the direction instantly.
What is a femtogray?
Femtogray (fGy) is a unit of radiation.
What is a rad?
Rad (rad) measures absorbed radiation dose. 'Radiation absorbed dose' — the US customary unit of absorbed radiation dose, fixed at exactly 0.01 gray. It is classified as a non-SI unit, still common in the US.
Is the femtogray to rad conversion exact?
Yes. 'Radiation absorbed dose' — the US customary unit of absorbed radiation dose, fixed at exactly 0.01 gray. That fixed definition is what the converter above uses, so any rounding you see is a display choice, not a limitation of the math.
What is the difference between rad vs. gray?
Both measure absorbed radiation dose; the gray is the modern SI unit while the rad is the older US customary unit, related by 1 gray = 100 rad exactly.