Equivalent Exposure Calculator
Fill in the values and the answer updates as you type.
How the Equivalent Exposure Calculator works
Exposure stays constant when ISO × time ÷ N² stays constant. So new time = old time × (new N² ÷ old N²) × (old ISO ÷ new ISO). Opening the aperture by one stop lets you halve the shutter time, and raising ISO by one stop does the same. This is the same trade-off every photographer makes when freezing motion or controlling depth of field. Example: Opening up from f/8 to f/4 at ISO 100 turns 1/125 s into 1/500 s, a change of 2 stops of aperture.
Inputs and results
The Equivalent Exposure Calculator takes 5 inputs and gives 3 results.
What you enter
- Current aperture (f/) — starts at 8.
- Current shutter (1 ÷ value) (1/s) — starts at 125.
- Current ISO — starts at 100.
- New aperture (f/) — starts at 4.
- New ISO — starts at 100.
What you get
- New shutter speed
- New shutter time (seconds)
- Aperture change (stops)
Example: Equivalent Exposure Calculator with the starting values
With current aperture 8 f/, current shutter (1 ÷ value) 125 1/s, current iso 100, new aperture 4 f/ and new iso 100, the calculator returns:
| New shutter speed | 1/500 s |
|---|---|
| New shutter time (seconds) | 0.002 |
| Aperture change (stops) | 2 |
Change any value above and the results update straight away.
Equivalent Exposure Calculator FAQ
How do I use the Equivalent Exposure Calculator?
Enter current aperture, current shutter (1 ÷ value), current iso and new aperture in the fields, then read new shutter speed, new shutter time (seconds) and aperture change (stops) 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 Equivalent Exposure Calculator calculate?
New shutter speed that keeps exposure the same after changing aperture or ISO. It returns new shutter speed, new shutter time (seconds) and aperture change (stops) from the 5 values you provide.
What values does the Equivalent Exposure Calculator start with?
It opens with current aperture 8 f/, current shutter (1 ÷ value) 125 1/s, current iso 100 and new aperture 4 f/ 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 Equivalent Exposure 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 Equivalent Exposure 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.