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To convert fm to meters: multiply by 10⁻¹⁵. To convert meters to fm: multiply by 10¹⁵.
1 fm = 10⁻¹⁵ m = 1,000 am = 10⁻⁶ nm. One meter equals 10¹⁵ femtometers.
For example, 1 Femtometer (fm) = 1000 Attometer (am).
| Femtometer (fm) | Attometer (am) |
|---|---|
| 0.1 | 100 |
| 0.5 | 500 |
| 1 | 1000 |
| 2 | 2000 |
| 5 | 5000 |
| 10 | 10000 |
| 25 | 25000 |
| 50 | 50000 |
| 100 | 100000 |
| 500 | 500000 |
| 1000 | 1000000 |
The femtometer is a unit of length equal to 10⁻¹⁵ meters, commonly used to measure the size of atomic nuclei.
1 fm = 10⁻¹⁵ m = 1,000 am = 10⁻⁶ nm. One meter equals 10¹⁵ femtometers.
To convert fm to meters: multiply by 10⁻¹⁵. To convert meters to fm: multiply by 10¹⁵.
Describing the size of protons (~0.87 fm radius) and nuclear diameters (1–15 fm depending on the element).
A proton's charge radius is approximately 0.87 fm. The diameter of a uranium-238 nucleus is about 15 fm.
Confusing femtometers with nanometers — a femtometer is one million times smaller than a nanometer.
Remember: atoms are ~0.1 nm, but nuclei are ~1–10 fm — nuclei are about 100,000 times smaller than the whole atom.
The attometer is an extremely small unit of length equal to 10⁻¹⁸ meters, or one quintillionth of a meter.
1 am = 10⁻¹⁸ m = 10⁻⁹ nm = 0.001 fm. One meter contains 10¹⁸ attometers.
To convert am to meters: multiply by 10⁻¹⁸. To convert meters to am: multiply by 10¹⁸.
Measuring quark interaction distances and the scale of fundamental particle phenomena.
The effective size of a quark is estimated at less than 1 attometer — far smaller than a proton (~1,000 am across).
Confusing attometers with angstroms (Å = 10⁻¹⁰ m). Attometers are 100 million times smaller than an angstrom.
Think of the prefix chain: milli (10⁻³), micro (10⁻⁶), nano (10⁻⁹), pico (10⁻¹²), femto (10⁻¹⁵), atto (10⁻¹⁸).



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