Shutter Speed Calculator - Aperture, ISO and EV Solver

A shutter speed calculator is a photography tool that turns the three legs of the exposure triangle - aperture, ISO, and the scene's exposure value - into the shutter time you dial in, or it works backwards to read the EV of a scene you have already metered.

• • Match Sunny 16 in low light: Compute the shutter speed that matches Sunny 16 when shooting indoors, where the same EV demands a much longer exposure at the same f-stop.
• • Plan handheld shutter speeds: Pick a shutter time at least 1 over the focal length in millimetres, then back-solve the aperture or ISO needed when light is dim.
• • Set up long exposures: Get the right shutter time for star trails or light painting by entering aperture, ISO, and EV and reading the snap-to-standard-stop result.
• • Confirm a metered EV: Enter the shutter, aperture, and ISO you used in the field and read the resulting EV to verify the camera's meter matched the lighting.

The exposure triangle is one of the first ideas a photographer learns, but the math is rarely memorised. A shutter speed calculator does the log base 2 arithmetic for you.

The tool returns both a raw seconds value and a snapped third-stop, so you can copy the number straight onto the camera dial.

If you are planning multi-hour shoots such as sunsets or star trails, the Time Lapse Calculator lives next to this one and uses the same exposure triangle inputs to schedule intervals.

The calculator uses the standard photographic exposure equation that relates f-number N, shutter time t, ISO, and exposure value.

• Aperture (N): Lens f-number such as 1.4, 2.8, 5.6, 8, 11, 16, or 22. Each full stop doubles or halves the light reaching the sensor.
• ISO: Sensor sensitivity. Doubling ISO adds 1 EV on the scale used by the calculator.
• Exposure value (EV): A scene descriptor where EV 15 is bright sun, EV 13 is light overcast, EV 9 is heavy overcast, EV 6 is indoor, and EV 0 is dim indoor.
• Shutter time (t): Exposure duration in seconds. Returned as a decimal and snapped to the nearest standard third-stop such as 1/125 s.

When you select 'Exposure value' as the target, the same formula runs in reverse. The calculator reads your shutter, aperture, and ISO, computes the raw EV, and shows you where that EV sits on a lighting scale.

The snapping step matters because camera dials only land on third-stop values. A raw 0.00781 s calculation rounds to 1/125 s, while a raw 1.18 s calculation snaps to 1 s or 1.3 s.

According to Wikipedia - Exposure Value, EV equals log base 2 of the f-number squared divided by shutter time, with ISO 100 as the reference sensitivity.

According to PhotoPills - Exposure Guide, PhotoPills pairs Sunny 16 with EV 15 at f/16 and ISO 100, matching the same exposure at 1/100 s.

When you preview exposures on a tablet before committing to a tripod, the Screen Size Calculator helps pick a viewing size that matches your image height in inches.

Four ideas drive every result. Understanding them helps you read the output as more than just a number.

These four ideas explain every output. Once you know that the math is log₂, that ISO 100 is the reference, that the result snaps to a camera-realistic value, and that stops can be traded between aperture, time, and ISO, the result becomes a starting point for creative choices.

RAW bursts at long shutter times can fill a memory card faster than expected, and the Data Transfer Calculator converts file size and connection speed into the minutes you need to offload the shoot.

Five quick steps move you from a blank form to a shutter time or an exposure value you can copy onto the camera.

1. 1 Pick the solve-for mode: Select 'Shutter speed' to find an exposure time, or 'Exposure value' to read the EV of a scene you already metered. The page swaps which inputs are highlighted.
2. 2 Enter aperture and ISO: Type the lens f-number and sensor ISO. Both fields default to f/8 and ISO 100 so you can change just one or two values when refining a base exposure.
3. 3 Enter EV or shutter time: In shutter mode, type the scene's EV - 15 for bright sun, 13 for light overcast, 9 for heavy overcast, 6 for indoor. In EV mode, type 0.008 for 1/125 s or 0.0166667 for 1/60 s.
4. 4 Read the snapped result: Read the primary shutter time, the snapped display string such as 1/125 s, the exposure value, the ISO shift from ISO 100, and the scene lighting context label.
5. 5 Apply or refine: Use the snapped value as a starting point, then adjust one leg of the exposure triangle at a time and re-run the calculator until the shutter speed matches your creative intent.

Set the mode to Shutter speed, enter f/5.6, ISO 200, and EV 9, then read the snapped shutter of 1/60 s. That is the same exposure as f/8 + 1/30 s + ISO 200 or f/4 + 1/125 s + ISO 200, so you can trade aperture and time to control depth of field or motion blur.

Once the shutter speeds are decided, the 3D Render Time Calculator estimates how long a stack of bracketed exposures will take to render if you composite them in software instead of in-camera.

The calculator saves time on log arithmetic and surfaces related information you would otherwise derive by hand.

• • Avoid mental log arithmetic: Photographers usually memorise EV charts for a few f-numbers. The calculator lets you dial in any aperture or ISO without flipping through tables or doing the log₂ in your head.
• • Match Sunny 16 and related rules: Sunny 16, Snowy 16, and Overcast 8 all map to fixed EV values. The calculator returns the matching shutter time across f-numbers and ISO settings.
• • Plan long exposures confidently: Astrophotography and night cityscapes need shutter times longer than the Bulb dial lists. The calculator extends to 30 s with snap-to-stop, enough for moonlit scenes.
• • Cross-check a metered EV: Enter the shutter, aperture, and ISO you shot with and read back the EV. Comparing that EV to a known scene descriptor tells you whether the camera's meter agreed with the lighting.
• • Trade stops without losing accuracy: Equivalent exposures share an EV, so the calculator makes it easy to swap one stop of aperture for one stop of time, or one stop of ISO, and read the new shutter time.

Together, the snapped shutter value, the EV readout, the ISO shift, and the lighting context give a small dossier for each shot. Photographers who shoot RAW recognise the same dossier from an EXIF inspector after the fact.

Cropping a long-exposure image for Instagram versus a 3:2 print uses a different aspect, and the Screen Ratio Calculator gives the numeric ratios you need before exporting.

The math is exact, but the real-world result depends on a few scene factors and a couple of model assumptions worth knowing.

• • The formula assumes the scene is metered at ISO 100. ISO below 100 extends the model slightly beyond the standard EV scale, so the snapped shutter value is a guideline rather than an exact dial reading.
• • Exposures longer than 30 s fall outside the snapping ladder. Bulb mode and external intervalometers are required, and the page clamps the upper bound at 30 s.
• • The calculator does not model scene reciprocity failure, a dim-light effect where long exposures on film or some older sensors need additional exposure compared with the linear log₂ prediction.

These caveats matter most for night work and studio photography. For daylight and indoor scenes with metered values, the result is within a third stop of what the dial needs.

According to Cambridge in Colour - Camera Exposure, EV 13 corresponds to light overcast, EV 9 to heavy overcast, and EV 6 to typical indoor lighting at f/2.8 and ISO 800.

Long exposures often arrive on a full memory card, and the Upload Time Calculator helps estimate the laptop transfer time once the shoot wraps.