Atto (a)
The SI prefix atto (a): a factor of 10⁻¹⁸, which is one quintillionth (10⁻¹⁸).
What is an atto unit?
- Symbol
- a
- Quantity
- SI Prefixes
- Unit system
- SI
- Definition
- The SI prefix atto (a): a factor of 10⁻¹⁸, which is one quintillionth (10⁻¹⁸).
- Exact
- Yes, the value is exact by definition
- Source
- SI Brochure, 9th edition (BIPM, 2019)
Common applications
Used for attoseconds, the time scale of electron motion. The 2023 Nobel Prize in Physics honored methods that generate attosecond light pulses.
Atto in other si prefixes units
- 1 a = 1e-48 QQuetta
- 1 a = 1e-45 RRonna
- 1 a = 1e-42 YYotta
- 1 a = 1e-39 ZZetta
- 1 a = 1e-36 EExa
- 1 a = 1e-33 PPeta
- 1 a = 1e-30 TTera
- 1 a = 1e-27 GGiga
- 1 a = 1e-24 MMega
- 1 a = 1e-21 kKilo
- 1 a = 1e-20 hHecto
- 1 a = 1e-19 daDeca
- 1 a = 1e-17 dDeci
- 1 a = 1e-16 cCenti
- 1 a = 1e-15 mMilli
- 1 a = 1e-12 µMicro
- 1 a = 1e-9 nNano
- 1 a = 0.000001 pPico
- 1 a = 0.001 fFemto
- 1 a = 1000 zZepto
- 1 a = 1000000 yYocto
- 1 a = 1000000000 rRonto
- 1 a = 1000000000000 qQuecto
- 1 a = 1e-18 ×1Base unit (no prefix)
Atto quick reference
| Atto | Kilo | Milli | Quetta |
|---|---|---|---|
| 1 a | = 1e-21 k | = 1e-15 m | = 1e-48 Q |
| 10 a | = 1e-20 k | = 1e-14 m | = 1e-47 Q |
| 100 a | = 1e-19 k | = 1e-13 m | = 1e-46 Q |
| 1000 a | = 1e-18 k | = 1e-12 m | = 1e-45 Q |
Where the atto unit fits
The next smaller si prefixes unit is the zepto unit (z). 1 a = 1000 z, and 1 z = 0.001 a.
The next larger si prefixes unit is the femto unit (f). 1 a = 0.001 f, and 1 f = 1000 a.
Frequently asked questions
- How many kilo units are in one atto unit?
- One atto unit = 1e-21 k (kilo units).
- How many milli units are in one atto unit?
- One atto unit = 1e-15 m (milli units).
- How many quetta units are in one atto unit?
- One atto unit = 1e-48 Q (quetta units).