Watts to photons per second
Type a value in W to get it in photons/s instantly.
1.279×10¹⁸photons/s
That's 426× as bright as a laser pointer, while a light bulb is 7.8× more. That is about 2.123 µmol of photons a second.
What it means
How many photons?
This counts photons arriving, not photons detected. A detector’s quantum efficiency decides how many of them are actually recorded.
The math
How to convert W to photons/s
Each photon carries E = hc ÷ λ, so photons per second = watts × λ(nm) ÷ 1.986 × 10⁻¹⁶. The figures below use the wavelength selected above.
Example: 1 W = 1.279×10¹⁸ photons/s.
The table below is for Ultraviolet, 254 nm.
Every unit
Your flux in every unit
Tables
W to photons/s conversion table
| W | photons/s |
|---|---|
| 1,000 W | 1.279×10²¹ photons/s |
| 1,000,000 W | 1.279×10²⁴ photons/s |
| 1×10⁹ W | 1.279×10²⁷ photons/s |
| 1×10¹² W | 1.279×10³⁰ photons/s |
| 1×10¹⁵ W | 1.279×10³³ photons/s |
| 1×10¹⁶ W | 1.279×10³⁴ photons/s |
| 1×10¹⁷ W | 1.279×10³⁵ photons/s |
| 1×10¹⁸ W | 1.279×10³⁶ photons/s |
| 1×10²⁰ W | 1.279×10³⁸ photons/s |
photons/s to W conversion table
| photons/s | W |
|---|---|
| 1,000 photons/s | 7.821×10⁻¹⁶ W |
| 1,000,000 photons/s | 7.821×10⁻¹³ W |
| 1×10⁹ photons/s | 7.821×10⁻¹⁰ W |
| 1×10¹² photons/s | 7.821×10⁻⁷ W |
| 1×10¹⁵ photons/s | 0.000782065 W |
| 1×10¹⁶ photons/s | 0.00782065 W |
| 1×10¹⁷ photons/s | 0.0782065 W |
| 1×10¹⁸ photons/s | 0.782065 W |
| 1×10²⁰ photons/s | 78.2065 W |
Quick answers
Quick answers
- How many photons/s is 1 W?
- 1 W is 1.279×10¹⁸ photons/s.
- How many photons/s is 10 W?
- 10 W is 1.279×10¹⁹ photons/s.
The units
About these units
Watts (W)
Optical power, for the wavelength selected.
Photons per second (photons/s)
The raw count of photons arriving each second.
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