Sunny 16 Calculator
Get correct exposure settings without a light meter, using the sunny 16 rule.
What is the sunny 16 rule?
The sunny 16 rule is a way to expose correctly without a meter: in bright sunlight, set the aperture to f/16 and the shutter speed to roughly one over your ISO. At ISO 100 that is about 1/100 s. It works because daylight is remarkably consistent, giving a scene brightness near EV 15.
Adjusting for other light
As the light softens, you open up: about one stop for slight overcast, two for cloudy, three for heavy overcast, and more for open shade. Pick the condition in the calculator and it shifts the exposure for you, then returns the shutter speed for whatever aperture you prefer.
Using sunny 16 on film and digital
Sunny 16 comes from the film era, where you could not check a screen, but the physics is identical on digital - it is a reliable manual starting point when a meter is fooled by snow, sand or backlight. Take the shot, check the histogram, and fine-tune from there.
How this calculation works
Formula: t = N² / (2^EV × ISO/100)
where:
N= aperture (f-number)EV= exposure valueISO= ISO sensitivity
Sources:
FAQ
Where does 'sunny 16' come from?
In bright sunlight at f/16 the correct shutter speed is about 1 divided by the ISO - 1/100 s at ISO 100, for example.
Is it accurate?
It's a reliable starting point outdoors, especially for film. Open up a stop or two as clouds roll in - which this tool does for you.
What settings do I use for other apertures?
Open up from f/16 and shorten the shutter to match; the tool recalculates the correct shutter speed for whichever aperture you enter.
Does sunny 16 work with digital cameras?
Yes. It is film-era guidance, but the physics is the same, so it gives a reliable manual starting point on any camera.