EV Calculator

An EV calculator works out the Exposure Value for a given camera setting. You pick three things, an aperture (f-stop), a shutter speed, and an ISO, and it returns a single number that describes how much light that combination lets in. The formula behind it is EV = log2(N squared divided by t) minus log2(ISO divided by 100), where N is the f-number and t is the shutter time in seconds. Our tool normalises the result to ISO 100 and shows it to one decimal place, so you can compare settings on a consistent scale. A higher EV means a brighter scene that needs less light; a lower EV means a darker one. Alongside the number, you get a short note about the kind of lighting that EV usually matches, which makes the figure easier to picture. It is free, runs in your browser, and needs no sign-up.

You reach for an exposure value calculator whenever you want to compare or plan settings instead of guessing. It is handy for learning the exposure triangle, because you can change one input and watch the EV move by exactly one stop. It helps when you shoot fully manual and want to check that a chosen aperture and shutter pair gives the brightness a scene calls for. It is also useful for matching an old light-meter reading, or for setting a baseline before you add exposure compensation. Photographers who use handheld or phone-based light meters often read an EV number from the meter, then use this kind of tool to find aperture and shutter combinations that hit it. Because the value is normalised to ISO 100, you can quickly see how bumping your ISO changes what light you actually need. In short, it turns three separate settings into one comparable number.

It takes three quick steps. First, choose your aperture from the f-stop dropdown, for example f/2.8 or f/16. Second, pick a shutter speed from its dropdown, such as 1/125 s or 1 second. Third, type your ISO in the number field, which defaults to 100. The result updates right away: you see the exposure value to one decimal place plus a short description of the lighting scene that EV typically fits. If you want to start over, the Reset Defaults button puts you back to f/16, 1/125 s, and ISO 100, which returns an EV of about 15, the classic bright-sun value. There is nothing to upload and no files to handle. You just pick values and read the answer. Our tool is free and needs no account, so you can experiment with as many combinations as you like without any limits or sign-up.

The core is the standard APEX definition: at ISO 100, EV = log2(N squared divided by t), where N is the f-number and t is the shutter time in seconds. So f/16 at 1/125 s gives log2(256 times 125), which rounds to 15.0. ISO changes the light a scene needs, so the tool subtracts log2(ISO divided by 100) to normalise everything back to ISO 100. That second term is why doubling your ISO from 100 to 200 lowers the ISO-100 EV by exactly 1. A worked check: f/2.8 at 1/60 s and ISO 100 comes out to about 8.9, which lines up with a brightly lit indoor space. Raise that to ISO 400 and the normalised value drops by two stops. Because everything is expressed in base-2 logarithms, each whole EV step equals one photographic stop, doubling or halving the light. That clean, one-number-per-stop behaviour is exactly what makes EV so useful for planning exposures.

ISO sets how sensitive the sensor is to light, so it shifts how much light a scene actually needs. Raising ISO means the same brightness can be captured with less exposure. In this calculator, the number is normalised to ISO 100, so a higher ISO produces a lower ISO-100 EV. The relationship is a clean doubling: going from ISO 100 to 200 lowers the normalised value by 1, and 100 to 400 lowers it by 2. For example, f/16 at 1/125 s reads about 15.0 at ISO 100, but around 13.0 at ISO 400, two stops lower. That is why ISO is often called the third leg of the exposure triangle. Aperture and shutter speed together set the EV; ISO shifts the light you need to reach a correct exposure. Keeping the value pinned to ISO 100 lets you compare any two settings on one scale, no matter what sensitivity you shot at, which is genuinely helpful when reviewing mixed sessions.

Equivalent exposures are different aperture and shutter combinations that let in the same total light, so they share the same EV. This is one of the most practical ideas in photography. Take f/2.8 at 1/500 s and f/4 at 1/250 s: both land at roughly EV 12 at ISO 100. Opening the aperture one stop while shortening the shutter one stop cancels out, so the brightness stays the same even though the look changes. That freedom lets you trade depth of field against motion blur without over or underexposing. Want a shallow, blurred background? Pick the wider aperture and a faster shutter. Want more in focus? Stop down and slow the shutter to match. You can test this in seconds with the calculator: change aperture and shutter in opposite directions by equal stops and watch the EV hold steady. Seeing the number stay put makes the trade-off concrete rather than abstract, which is a fast way to build real intuition.

The EV number itself is exact for the settings you enter, since it comes straight from the standard formula and is rounded to one decimal place. The scene descriptions, though, are approximate by nature. Real light varies with weather, time of day, reflections, and subject, so any chart of typical EV values is a guide, not a rule. As rough anchors, bright sun sits near EV 15, an overcast day near 12, sunset or open shade around 10, bright indoors about 8, a typical home interior near 7, and night scenes drop low or even negative. Treat these as starting points and confirm with your camera meter or a handheld meter for anything important. The calculator is a planning and learning aid, not a replacement for metering the actual scene in front of you. Used that way, it gives you a reliable reference frame and helps you reason about settings before you even lift the camera.

No. This is a pure calculator, not a converter or editor, so there are no files involved at all. You do not upload images, install software, or create an account. You simply choose an aperture and shutter speed from the dropdowns, type an ISO, and read the exposure value on screen. Everything happens right in your browser, and the numbers you enter are just used to compute the result on the spot. That makes it fast and private, since nothing is being sent anywhere for processing the way an image tool would send a photo. Because it is free and needs no sign-up, you can open it any time you want to sanity-check a setting, plan a shot, or teach yourself how the exposure triangle behaves. Keep it bookmarked next to your other reference tools. When you are ready to actually meter a scene, use it as a companion to your camera rather than a substitute for it.

They sound similar but do different jobs. Exposure Value is an absolute measure: it describes how much light a specific aperture, shutter, and ISO combination admits, expressed as one number. Exposure compensation is a relative nudge you apply on top of what your camera meter suggests, usually in third or half stops, to make an image brighter or darker than the meter's default. The meter can be fooled by very bright or very dark subjects, so compensation lets you override it deliberately. Think of EV as the reading and compensation as the correction. This calculator deals with EV, the underlying value, so it helps you understand the baseline before any compensation enters the picture. Once you know the EV of a setting, adding plus or minus one stop of compensation is the same as shifting that EV by one, which is another reason the single-number scale is so handy. Learn EV first, and compensation becomes far easier to reason about.

Yes, and that pairing is where EV really earns its keep. Many handheld and phone-based light meters report an EV number directly. You read the EV off the meter, then use a calculator like this one to find aperture and shutter combinations that hit it at your chosen ISO. The Sunny 16 rule is a meterless shortcut that fits neatly with EV: in bright, direct sun the scene sits at about EV 15 at ISO 100, which is why f/16 at roughly 1/125 s is the classic go-to. From that anchor you can reason your way to other conditions by counting stops, dropping a few EV for overcast, more for shade, and so on. Enter those settings here and confirm the number matches your expectation. Used together, a meter reading, the Sunny 16 anchor, and this calculator give you a fast, reliable way to nail exposure in the field, even before you trust your eye. It is a genuinely practical loop for manual shooters.