FlashFlashApp

Set your aperture — get the power. Set the power — get the aperture. The Guide Number formula, solved instantly. Works anywhere you shoot.

Know your flash settings before you shoot — not after three test frames.

FlashFlash is a manual flash calculator built on the Guide Number method. It solves in both directions:

POWER CALCULATOR Set your aperture. FlashFlash tells you exactly what power fraction to dial in — 1/4, 1/16, whatever the shot needs.

APERTURE RECOMMENDER Set your power level. FlashFlash tells you exactly which f-stop to use. Battery-constrained, locked into a specific power level, planning a shot before you arrive — this is the tab for it.

No test shots. No chimping. Enter your settings, read the answer, nail the exposure.

WHAT YOU ENTER · Guide Number — type it manually or pick from 100+ built-in presets (Godox, Canon, Nikon, Sony, Profoto, Elinchrom, and more) · ISO · Aperture or power level — depending which tab you're on · Flash-to-subject distance · Flash zoom from 24 mm to 200 mm · Filter compensation for gels, diffusers, and softboxes

WHAT YOU GET · The exact power fraction or f-stop, snapped to a real standard setting · Effective GN and Required GN — so you know exactly how much headroom you have · A live scene visualization: your flash, your subject, your light cone, updating in real time · A power bar showing at a glance how hard your flash is working

ON CAMERA OR OFF FlashFlash always asks for flash-to-subject distance — not camera-to-subject. Because when your flash is on a stand three feet from your subject and you are eight feet away, those numbers are not the same. And that difference is everything.

FULLY OFFLINE No account. No network connection. No subscription. One purchase. Your settings are saved on your device. Works anywhere you shoot.