Sunny 16 Rule Calculator
The Sunny 16 rule sets a good exposure in bright sun without a light meter: at f/16 the shutter is one over the ISO. Enter your ISO to see that base shutter, then pick a lighting preset or type an aperture to get the equivalent shutter that holds the same exposure. Opening up from f/16 to f/8, for example, lets in four times the light and needs a shutter four times faster.
How to use the Sunny 16 calculator
- Enter your ISO or tap an ISO preset such as 100 or 400.
- Tap a lighting preset from bright sun to open shade, or type an aperture f-number.
- Read the base shutter at f/16, which is one over your ISO.
- Read the equivalent shutter at your chosen aperture on the second card.
- Press Copy to save the settings line.
Examples
Bright sun at ISO 100
ISO 100, f/16
base shutter 1/100 s at f/16
Open up to f/8
ISO 100, f/8
1/400 s (two stops faster than f/16)
Bright sun at ISO 200
ISO 200, f/16
base shutter 1/200 s at f/16
Frequently asked questions
What is the Sunny 16 rule?
On a bright sunny day, a correct exposure at f/16 uses a shutter speed of one over the ISO. At ISO 100 that is 1/100 second, and at ISO 200 it is 1/200 second. It gives a meter-free starting point that is remarkably reliable in strong sun.
How do I adjust for clouds or shade?
Open the aperture as the light drops: f/11 for slight overcast, f/8 for overcast, f/5.6 for heavy overcast and f/4 for open shade. The lighting presets set these apertures for you while the tool keeps the exposure matched.
How does changing the aperture change the shutter?
Light scales with one over the f-number squared, so the equivalent shutter is the base shutter times the f-number over 16, squared. Opening from f/16 to f/8 is two stops, which makes the shutter four times faster.
Why use Sunny 16 if my camera has a meter?
It is a fast sanity check and a fallback when a meter is fooled by snow, backlight or a bright sky. It also trains your intuition for how aperture, shutter and ISO trade off in stops.
Does Sunny 16 work at any ISO?
Yes. The base shutter scales directly with ISO, so at ISO 400 the f/16 shutter is 1/400 second and the preset apertures behave the same way relative to f/16. The rule is proportional, not tied to one ISO.
My camera has no exact 1/ISO shutter. What then?
Round to the nearest available speed. Many cameras offer 1/125 rather than 1/100, which is close enough for a starting exposure, and you can nudge aperture or ISO by a fraction of a stop to fine-tune.
Do the lighting presets cover every condition?
They span bright sun through open shade in one-stop steps, which handles most daylight. Deep shade, sunrise, sunset and indoor light fall outside the rule, where a meter or exposure bracketing serves better.
Is anything uploaded?
No. The exposure math runs in your browser, so the ISO and aperture you enter stay on your device.
Learn more
- The Sunny 16 rule and its cloudy-day cousins
How one rule of thumb sets daylight exposure, why each weather step opens the aperture one stop, and where it stops working.
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