Exposure Value Calculator
Enter an aperture f-number and a shutter speed in seconds to get the exposure value (EV) — the single number that ties every camera exposure together.
Enter shutter as seconds
Type the shutter speed as a decimal in seconds — 0.004 for 1/250 s, 0.0625 for 1/16 s — not as a fraction.
What is exposure value?
One number for aperture and shutter speed
The exposure value, or EV, is a single number that describes how much light a given camera setting lets reach the sensor. An exposure value calculator takes two settings — the aperture as an f-number (N) and the shutter speed in seconds (t) — and combines them with the formula EV = log₂(N² ÷ t). Because it folds both controls into one figure, EV makes it easy to see that very different settings can be equivalent, and that each whole step of EV halves or doubles the light. Photographers use it to compare exposures, read light-meter values, and reason about the exposure triangle.
Enter an aperture f-number and a shutter speed in seconds to get the exposure value (EV) instantly.
The exposure value is the base-2 logarithm of the f-number squared divided by the shutter speed in seconds. Squaring the f-number reflects that the aperture controls light by area, while dividing by the shutter speed accounts for how long the light is collected.
EV = log₂(N² ÷ t)Because the result is a base-2 logarithm, every increase of one EV means half as much light reaches the sensor, and every decrease of one EV means twice as much. That is why EV is such a compact way to talk about exposure: one number, and each step is a clean stop of light.
Suppose you shoot at f/4 with a shutter speed of 1/16 s, which is 0.0625 s.
Square the f-number
4² = 16 — the aperture term, since light scales with the square of the f-number.
Divide by the shutter speed
16 ÷ 0.0625 = 256 — the ratio of aperture area to shutter speed.
Take the base-2 logarithm
log₂(256) = 8 — the exposure value, because 2⁸ = 256.
A single exposure value describes a whole family of equivalent settings, not one fixed pair. EV 8 is reached by f/4 at 1/16 s, but also by f/2.8 at 1/32 s or f/5.6 at 1/8 s — each combination lets the same total light through, so all of them sit at EV 8. That is the practical heart of the exposure triangle: open the aperture one stop and you can shorten the shutter speed one stop to keep the same exposure. The scale is logarithmic, so the gap between EV 8 and EV 9 is one stop of light, not one unit on a linear ruler — EV 9 lets in half the light of EV 8. Higher EVs mean brighter scenes (bright daylight sits around EV 15), while low and negative EVs describe dim scenes (a moonlit landscape can fall below EV 0). Reading EV this way lets you trade aperture against shutter speed with confidence and match a meter reading to settings that produce a correct exposure.
The formula is exact, but a couple of practical points are worth keeping in mind.
EV is defined at ISO 100 and excludes sensitivity
This exposure value is the standard EV defined at ISO 100 and depends only on the aperture and shutter speed — it does not include the ISO sensitivity or the actual scene brightness. To match a real scene you would combine this EV with the metered light level and any ISO offset. Enter the shutter speed as a decimal in seconds (1/250 s is 0.004), and remember that a higher EV means less light, not more.