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Light Falloff Calculator
How much light you lose when you move a light farther away.
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How it 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.
FAQ
Is this calculator free?
Yes. No signup is needed and nothing you enter is stored.
Is the result exact?
Results are rounded for display. For financial, medical, or legal decisions, confirm with a professional.
Do my numbers leave my device?
No. The calculation runs in your browser.