Exposure Value (EV) Calculator
Fill in the values and the answer updates as you type.
How the Exposure Value (EV) Calculator works
EV = log2(N² ÷ t), where N is the f-number and t is the shutter time in seconds. Each +1 EV halves the light, and ISO shifts the value by log2(ISO ÷ 100). Enter the shutter speed as its denominator, so 125 means 1/125 s, and 0.5 means a 2 second exposure. Lux uses the common incident-meter constant of 2.5. Example: f/8 at 1/125 s and ISO 100 gives EV 13, which is about 20,000 lux.
Inputs and results
The Exposure Value (EV) Calculator takes 3 inputs and gives 3 results.
What you enter
- Aperture (f-number) (f/) — starts at 8.
- Shutter speed (1 ÷ this value) (1/s) — starts at 125.
- ISO — starts at 100.
What you get
- Exposure value at ISO 100 (EV)
- Exposure value at your ISO (EV)
- Approx. scene illuminance (lux)
Example: Exposure Value (EV) Calculator with the starting values
With aperture (f-number) 8 f/, shutter speed (1 ÷ this value) 125 1/s and iso 100, the calculator returns:
| Exposure value at ISO 100 (EV) | 13 |
|---|---|
| Exposure value at your ISO (EV) | 13 |
| Approx. scene illuminance (lux) | 20,000 |
Change any value above and the results update straight away.
Exposure Value (EV) Calculator FAQ
How do I use the Exposure Value (EV) Calculator?
Enter aperture (f-number), shutter speed (1 ÷ this value) and iso in the fields, then read exposure value at iso 100 (ev), exposure value at your iso (ev) and approx. scene illuminance (lux) in the result panel. The answer updates as you type, and you can press Calculate or Enter to refresh it. Use “Copy link” to share your exact numbers with someone else.
What does the Exposure Value (EV) Calculator calculate?
Convert aperture, shutter speed, and ISO into an exposure value. It returns exposure value at iso 100 (ev), exposure value at your iso (ev) and approx. scene illuminance (lux) from the 3 values you provide.
What values does the Exposure Value (EV) Calculator start with?
It opens with aperture (f-number) 8 f/, shutter speed (1 ÷ this value) 125 1/s and iso 100 so you can see a working result straight away. Replace them with your own numbers, or press Reset to return to these starting values.
Is the Exposure Value (EV) Calculator free and private?
Yes. It is free, needs no account, and runs in your browser, so nothing you type is sent to or stored on our servers. See the Privacy Policy for details.
Can I rely on the Exposure Value (EV) Calculator for important decisions?
Treat the result as a well-rounded estimate. Real situations often have details a general calculator cannot know, so confirm important decisions with a qualified professional. See the Disclaimer for more.