Aperture, Shutter Speed, ISO Calculator

Correct exposure for any lighting condition comes from the three variables of the exposure triangle: aperture, shutter speed, and ISO. The exposure value (EV) can be computed from all three settings, or any single missing variable can be solved for once the other two and a target EV are known.

• Calculating EV finds the exposure value from all three settings; solving for aperture, shutter speed, or ISO finds whichever one is missing when a target EV is given.
• Standard f-stops from f/1 to f/64 are available for aperture, with custom entry accepting any f-number, including third-stop values such as 6.3 or 3.2.
• Shutter speed ranges from 1/4000 second to 60 seconds among the standard values, with custom entry accepting fractions such as 1/320 or decimals such as 0.5.
• ISO sensitivity runs from 25 to 102400 among the standard values, with a custom number accepted as well.
• A target EV is needed when solving for a variable. As a reference, bright sunlight sits around EV 15, overcast skies around EV 10, and dim indoor lighting around EV 5.
• A step-by-step derivation is available, applying the formula EV = log2(100 * aperture^2 / (ISO * shutter speed)).
• Equivalent exposures shows alternative aperture, shutter speed, and ISO combinations that produce the same exposure value.

An aperture of f/16 at ISO 100 and a shutter speed of 1/100 second gives EV = log2(100 x 16^2 / (100 x 0.01)) = log2(25600) ≈ 14.6, close to the reference value of EV 15 for bright sunlight (the classic "Sunny 16" setting). Widening the aperture to f/8, two stops down, would need a four-times-faster shutter or a quarter of the ISO to land on the same EV.

The exposure triangle calculator applies across a wide range of photography scenarios, from planning a shoot in advance to recovering from unexpected lighting in the field. Photographers at every skill level benefit from a clear mathematical view of how aperture, shutter speed, and ISO interact to determine exposure.

• Landscape photography: Calculate the required shutter speed for a waterfall scene at f/16 and ISO 100. Whether a neutral density filter is needed depends on whether the solved shutter speed exceeds a handheld limit.
• Astrophotography: Set a target EV of -6 for the Milky Way and solve for the ISO that pairs with a wide aperture such as f/1.4 and a 20-second exposure dictated by the 500 rule.
• Sports and action: Lock in a fast shutter speed such as 1/1000 second and solve for the aperture and ISO combination that achieves correct exposure under stadium lighting at roughly EV 8.
• Portrait photography: A wide aperture such as f/2.8 gives shallow depth of field; solving for shutter speed at a preferred ISO keeps handheld results sharp.
• Education: Equivalent exposures make the exposure triangle visible and intuitive. Changing aperture by one stop and compensating with shutter speed produces identical exposure values.
• Film photography: Pre-calculate exposure settings for a film stock with a fixed ISO. Entering the film speed and the target EV for the shooting environment finds a workable aperture and shutter combination before loading the roll.
• Video production: Solve for aperture or ISO when the shutter is constrained by the 180-degree rule. For 24 fps footage, the shutter is locked at 1/48 second, so the other two variables must adapt.
• Event photography: Adapt quickly to changing lighting by solving for whichever variable needs to move for a new target EV, leaving the others fixed for consistency.