Flash ISO Calculator
Calculate required ISO for a flash exposure at a given distance.
Calculator
Enter the values below. Every quantity identifies its unit or meaning.
How to use this calculator
What to enter
Enter or select the following as requested: Guide number at ISO 100; Aperture (f-number); Flash distance (m). Follow the units, valid ranges, examples, and options displayed beside each field.
What the result means
The imaging or media result estimates dimensions, exposure relationships, storage, bitrate, field of view, or transfer time from the camera, file, lens, or encoding values entered. Check units, sensor/crop assumptions, codec, frame rate, compression, and whether the result is theoretical or based on actual file metadata.
When to use it
Use this to plan camera settings, storage, export quality, or media transfer. Treat calculated file sizes and exposure outcomes as estimates when the camera, codec, scene, or platform may vary.