⚡ Flash Guide Number Calculator
GN to distance/aperture calculations
Maximum Flash Distance @ f/5.6
6.4m
meters
21.1ft
feet
GN @ ISO 100
36.0m / 118.1ft
ISO Adjustment
×1.00
📸 Flash Settings
💡 Power Level Guide
| Power | GN (m) | Max Distance @ f/5.6 | Light Loss |
|---|---|---|---|
| 1/1 | 36.0 | 6.4m | 0 stops |
| 1/2 | 25.5 | 4.5m | -0.5 stops |
| 1/4 | 18.0 | 3.2m | -1.0 stops |
| 1/8 | 12.7 | 2.3m | -1.5 stops |
| 1/16 | 9.0 | 1.6m | -2.0 stops |
| 1/32 | 6.4 | 1.1m | -2.5 stops |
| 1/64 | 4.5 | 0.8m | -3.0 stops |
| 1/128 | 3.2 | 0.6m | -3.5 stops |
📖 Aperture Quick Reference
f/2.8
12.9m
f/4
9.0m
f/5.6
6.4m
f/8
4.5m
f/11
3.3m
f/16
2.3m
📐 Guide Number Formula
GN = Distance × Aperture
Distance = GN ÷ Aperture
Aperture = GN ÷ Distance
GN at new ISO = GN × √(new ISO / 100)