Exposure Calculator
Turn aperture, shutter speed and ISO into an exposure value, normalized to ISO 100, and find the matching shutter speed when you change aperture or ISO. Calculated in your browser.
Exposure value (EV₁₀₀)
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Show the math
Exposure value combines aperture N and shutter time t; EV₁₀₀ normalizes it to ISO 100 so brightness can be compared:
EV = log₂(N² ÷ t)
EV100 = EV − log₂(ISO ÷ 100)
new t = t · (ISO ÷ newISO) · (newN ÷ N)²
Enter shutter speed as a fraction like 1/250 or as whole seconds. All math runs in your browser.
What this does
An exposure calculator turns aperture, shutter speed, and ISO into an exposure value normalized to ISO 100, and finds the matching shutter speed when you change aperture or ISO.
How to use it
- Enter aperture, shutter, and ISO.
- Read the exposure value.
- Change aperture or ISO.
- Read the matching shutter speed.
How it works
EV combines aperture and shutter; EV₁₀₀ normalizes to ISO 100 so brightness compares regardless of ISO. Equivalent exposures keep N² ÷ t constant after ISO scaling.
EV = log₂(N² ÷ t)
Understanding your result
The point of EV is that many combinations of aperture and shutter give the same brightness, so the calculator shows the equivalent settings, freeing you to choose for effect: a wide aperture for shallow depth, a fast shutter to freeze motion, low ISO for clean files. Changing one stop in aperture, shutter, or ISO is balanced by an opposite stop in another, which is the exposure triangle in action.
Example
f/8 at 1/250 s is about EV 14 (13.97) at ISO 100; opening to f/5.6 needs 1/510 s, roughly 1/500 s, to match.
Last updated .
Frequently asked questions
What is exposure value (EV)?
EV combines aperture and shutter speed as log₂(N²/t). EV₁₀₀ normalizes that to ISO 100 so scene brightness can be compared regardless of the ISO that was set.
How does the matching shutter speed work?
It keeps the exposure constant when you change aperture or ISO: new t = t · (ISO ÷ newISO) · (newN ÷ N)². Enter shutter speed as a fraction like 1/250 or as whole seconds.
Is anything uploaded?
No. The calculation runs entirely in your browser — nothing you enter is stored or sent.
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