How it works
Fill in the 2 fields above and Flash Guide Number Calculator calculates the result instantly, recalculating as you change any value. It applies the formula f = GN / distance. The math runs locally in your browser — nothing is sent to a server.
Formula
f = GN / distanceExamples
- Guide number 40, Distance 5 m → Aperture: f/8
Frequently asked questions
How do I use the Flash Guide Number Calculator?
Enter your values in the 2 input fields and the result is calculated automatically as you type. Change any value to see the numbers update instantly.
What formula does the Flash Guide Number Calculator use?
It uses f = GN / distance. The calculation is performed in your browser using standard, well-established math for accurate results.
Is my data private?
Yes. The Flash Guide Number Calculator runs entirely in your browser. Nothing you enter is uploaded, saved to a server, or shared — it never leaves your device.
Is the Flash Guide Number Calculator free?
Yes, it is completely free with no sign-up, no limits and no watermarks. Like every tool on photography and the rest of the platform, you can use it as often as you like.
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