Light Falloff Calculator
Fill in the values and the answer updates as you type.
How the Light Falloff Calculator works
Light intensity follows the inverse square law: it is proportional to 1 ÷ distance². Doubling the distance leaves one quarter of the light, which is two stops. Moving a light 1.41 times farther costs exactly one stop. This is why a close softbox gives a quick, strong falloff and a distant one gives even light across a scene. Example: Moving a light from 1 m to 2 m leaves 25% of the light, a change of -2 stops.
Inputs and results
The Light Falloff Calculator takes 2 inputs and gives 3 results.
What you enter
- Current distance to subject (m) — starts at 1.
- New distance to subject (m) — starts at 2.
What you get
- Light remaining
- Light change (stops)
- Distance for one stop less (m)
Example: Light Falloff Calculator with the starting values
With current distance to subject 1 m and new distance to subject 2 m, the calculator returns:
| Light remaining | 25% |
|---|---|
| Light change (stops) | -2 |
| Distance for one stop less (m) | 1.41 |
Change any value above and the results update straight away.
Light Falloff Calculator FAQ
How do I use the Light Falloff Calculator?
Enter current distance to subject and new distance to subject in the fields, then read light remaining, light change (stops) and distance for one stop less (m) 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 Light Falloff Calculator calculate?
How much light you lose when you move a light farther away. It returns light remaining, light change (stops) and distance for one stop less (m) from the 2 values you provide.
What values does the Light Falloff Calculator start with?
It opens with current distance to subject 1 m and new distance to subject 2 m 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 Light Falloff 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 Light Falloff 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.