Flash Guide Number Distance Calculator
Calculate flash working distance from guide number, aperture, and ISO for manual flash photography.
GN 36 m, f/1.4, ISO 100 =
25.71 m flash distance
Representative value from the Flash Guide Number Distance Calculator reference table.
Reference Values
Browse 144 reference values with individual detail pages for quick lookup.
Flash Guide Number Distance Calculator
Estimate flash-to-subject distance for manual flash exposure using guide number, aperture, and ISO.
Estimated Flash Distance
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Reference Table
Use this complete table for quick lookup and internal linking to specific value pages.
| Flash Scenario | Distance (m) | Distance (ft) |
|---|---|---|
| GN 12 m, f/1.4, ISO 100 | 8.57 m flash distance | 28.12 |
| GN 12 m, f/1.4, ISO 200 | 12.12 m flash distance | 39.77 |
| GN 12 m, f/1.4, ISO 400 | 17.14 m flash distance | 56.24 |
| GN 12 m, f/2, ISO 100 | 6 m flash distance | 19.69 |
| GN 12 m, f/2, ISO 200 | 8.49 m flash distance | 27.84 |
| GN 12 m, f/2, ISO 400 | 12 m flash distance | 39.37 |
| GN 12 m, f/2.8, ISO 100 | 4.29 m flash distance | 14.06 |
| GN 12 m, f/2.8, ISO 200 | 6.06 m flash distance | 19.88 |
| GN 12 m, f/2.8, ISO 400 | 8.57 m flash distance | 28.12 |
| GN 12 m, f/4, ISO 100 | 3 m flash distance | 9.84 |
| GN 12 m, f/4, ISO 200 | 4.24 m flash distance | 13.92 |
| GN 12 m, f/4, ISO 400 | 6 m flash distance | 19.69 |
| GN 12 m, f/5.6, ISO 100 | 2.14 m flash distance | 7.03 |
| GN 12 m, f/5.6, ISO 200 | 3.03 m flash distance | 9.94 |
| GN 12 m, f/5.6, ISO 400 | 4.29 m flash distance | 14.06 |
| GN 12 m, f/8, ISO 100 | 1.5 m flash distance | 4.92 |
| GN 12 m, f/8, ISO 200 | 2.12 m flash distance | 6.96 |
| GN 12 m, f/8, ISO 400 | 3 m flash distance | 9.84 |
| GN 12 m, f/11, ISO 100 | 1.09 m flash distance | 3.58 |
| GN 12 m, f/11, ISO 200 | 1.54 m flash distance | 5.06 |
| GN 12 m, f/11, ISO 400 | 2.18 m flash distance | 7.16 |
| GN 12 m, f/16, ISO 100 | 0.75 m flash distance | 2.46 |
| GN 12 m, f/16, ISO 200 | 1.06 m flash distance | 3.48 |
| GN 12 m, f/16, ISO 400 | 1.5 m flash distance | 4.92 |
| GN 20 m, f/1.4, ISO 100 | 14.29 m flash distance | 46.87 |
| GN 20 m, f/1.4, ISO 200 | 20.2 m flash distance | 66.28 |
| GN 20 m, f/1.4, ISO 400 | 28.57 m flash distance | 93.74 |
| GN 20 m, f/2, ISO 100 | 10 m flash distance | 32.81 |
| GN 20 m, f/2, ISO 200 | 14.14 m flash distance | 46.4 |
| GN 20 m, f/2, ISO 400 | 20 m flash distance | 65.62 |
| GN 20 m, f/2.8, ISO 100 | 7.14 m flash distance | 23.43 |
| GN 20 m, f/2.8, ISO 200 | 10.1 m flash distance | 33.14 |
| GN 20 m, f/2.8, ISO 400 | 14.29 m flash distance | 46.87 |
| GN 20 m, f/4, ISO 100 | 5 m flash distance | 16.4 |
| GN 20 m, f/4, ISO 200 | 7.07 m flash distance | 23.2 |
| GN 20 m, f/4, ISO 400 | 10 m flash distance | 32.81 |
| GN 20 m, f/5.6, ISO 100 | 3.57 m flash distance | 11.72 |
| GN 20 m, f/5.6, ISO 200 | 5.05 m flash distance | 16.57 |
| GN 20 m, f/5.6, ISO 400 | 7.14 m flash distance | 23.43 |
| GN 20 m, f/8, ISO 100 | 2.5 m flash distance | 8.2 |
| GN 20 m, f/8, ISO 200 | 3.54 m flash distance | 11.6 |
| GN 20 m, f/8, ISO 400 | 5 m flash distance | 16.4 |
| GN 20 m, f/11, ISO 100 | 1.82 m flash distance | 5.97 |
| GN 20 m, f/11, ISO 200 | 2.57 m flash distance | 8.44 |
| GN 20 m, f/11, ISO 400 | 3.64 m flash distance | 11.93 |
| GN 20 m, f/16, ISO 100 | 1.25 m flash distance | 4.1 |
| GN 20 m, f/16, ISO 200 | 1.77 m flash distance | 5.8 |
| GN 20 m, f/16, ISO 400 | 2.5 m flash distance | 8.2 |
| GN 28 m, f/1.4, ISO 100 | 20 m flash distance | 65.62 |
| GN 28 m, f/1.4, ISO 200 | 28.28 m flash distance | 92.8 |
| GN 28 m, f/1.4, ISO 400 | 40 m flash distance | 131.23 |
| GN 28 m, f/2, ISO 100 | 14 m flash distance | 45.93 |
| GN 28 m, f/2, ISO 200 | 19.8 m flash distance | 64.96 |
| GN 28 m, f/2, ISO 400 | 28 m flash distance | 91.86 |
| GN 28 m, f/2.8, ISO 100 | 10 m flash distance | 32.81 |
| GN 28 m, f/2.8, ISO 200 | 14.14 m flash distance | 46.4 |
| GN 28 m, f/2.8, ISO 400 | 20 m flash distance | 65.62 |
| GN 28 m, f/4, ISO 100 | 7 m flash distance | 22.97 |
| GN 28 m, f/4, ISO 200 | 9.9 m flash distance | 32.48 |
| GN 28 m, f/4, ISO 400 | 14 m flash distance | 45.93 |
| GN 28 m, f/5.6, ISO 100 | 5 m flash distance | 16.4 |
| GN 28 m, f/5.6, ISO 200 | 7.07 m flash distance | 23.2 |
| GN 28 m, f/5.6, ISO 400 | 10 m flash distance | 32.81 |
| GN 28 m, f/8, ISO 100 | 3.5 m flash distance | 11.48 |
| GN 28 m, f/8, ISO 200 | 4.95 m flash distance | 16.24 |
| GN 28 m, f/8, ISO 400 | 7 m flash distance | 22.97 |
| GN 28 m, f/11, ISO 100 | 2.55 m flash distance | 8.35 |
| GN 28 m, f/11, ISO 200 | 3.6 m flash distance | 11.81 |
| GN 28 m, f/11, ISO 400 | 5.09 m flash distance | 16.7 |
| GN 28 m, f/16, ISO 100 | 1.75 m flash distance | 5.74 |
| GN 28 m, f/16, ISO 200 | 2.47 m flash distance | 8.12 |
| GN 28 m, f/16, ISO 400 | 3.5 m flash distance | 11.48 |
| GN 36 m, f/1.4, ISO 100 | 25.71 m flash distance | 84.36 |
| GN 36 m, f/1.4, ISO 200 | 36.37 m flash distance | 119.31 |
| GN 36 m, f/1.4, ISO 400 | 51.43 m flash distance | 168.73 |
| GN 36 m, f/2, ISO 100 | 18 m flash distance | 59.06 |
| GN 36 m, f/2, ISO 200 | 25.46 m flash distance | 83.52 |
| GN 36 m, f/2, ISO 400 | 36 m flash distance | 118.11 |
| GN 36 m, f/2.8, ISO 100 | 12.86 m flash distance | 42.18 |
| GN 36 m, f/2.8, ISO 200 | 18.18 m flash distance | 59.65 |
| GN 36 m, f/2.8, ISO 400 | 25.71 m flash distance | 84.36 |
| GN 36 m, f/4, ISO 100 | 9 m flash distance | 29.53 |
| GN 36 m, f/4, ISO 200 | 12.73 m flash distance | 41.76 |
| GN 36 m, f/4, ISO 400 | 18 m flash distance | 59.06 |
| GN 36 m, f/5.6, ISO 100 | 6.43 m flash distance | 21.09 |
| GN 36 m, f/5.6, ISO 200 | 9.09 m flash distance | 29.83 |
| GN 36 m, f/5.6, ISO 400 | 12.86 m flash distance | 42.18 |
| GN 36 m, f/8, ISO 100 | 4.5 m flash distance | 14.76 |
| GN 36 m, f/8, ISO 200 | 6.36 m flash distance | 20.88 |
| GN 36 m, f/8, ISO 400 | 9 m flash distance | 29.53 |
| GN 36 m, f/11, ISO 100 | 3.27 m flash distance | 10.74 |
| GN 36 m, f/11, ISO 200 | 4.63 m flash distance | 15.18 |
| GN 36 m, f/11, ISO 400 | 6.55 m flash distance | 21.47 |
| GN 36 m, f/16, ISO 100 | 2.25 m flash distance | 7.38 |
| GN 36 m, f/16, ISO 200 | 3.18 m flash distance | 10.44 |
| GN 36 m, f/16, ISO 400 | 4.5 m flash distance | 14.76 |
| GN 43 m, f/1.4, ISO 100 | 30.71 m flash distance | 100.77 |
| GN 43 m, f/1.4, ISO 200 | 43.44 m flash distance | 142.51 |
| GN 43 m, f/1.4, ISO 400 | 61.43 m flash distance | 201.54 |
| GN 43 m, f/2, ISO 100 | 21.5 m flash distance | 70.54 |
| GN 43 m, f/2, ISO 200 | 30.41 m flash distance | 99.76 |
| GN 43 m, f/2, ISO 400 | 43 m flash distance | 141.08 |
| GN 43 m, f/2.8, ISO 100 | 15.36 m flash distance | 50.38 |
| GN 43 m, f/2.8, ISO 200 | 21.72 m flash distance | 71.25 |
| GN 43 m, f/2.8, ISO 400 | 30.71 m flash distance | 100.77 |
| GN 43 m, f/4, ISO 100 | 10.75 m flash distance | 35.27 |
| GN 43 m, f/4, ISO 200 | 15.2 m flash distance | 49.88 |
| GN 43 m, f/4, ISO 400 | 21.5 m flash distance | 70.54 |
| GN 43 m, f/5.6, ISO 100 | 7.68 m flash distance | 25.19 |
| GN 43 m, f/5.6, ISO 200 | 10.86 m flash distance | 35.63 |
| GN 43 m, f/5.6, ISO 400 | 15.36 m flash distance | 50.38 |
| GN 43 m, f/8, ISO 100 | 5.38 m flash distance | 17.63 |
| GN 43 m, f/8, ISO 200 | 7.6 m flash distance | 24.94 |
| GN 43 m, f/8, ISO 400 | 10.75 m flash distance | 35.27 |
| GN 43 m, f/11, ISO 100 | 3.91 m flash distance | 12.83 |
| GN 43 m, f/11, ISO 200 | 5.53 m flash distance | 18.14 |
| GN 43 m, f/11, ISO 400 | 7.82 m flash distance | 25.65 |
| GN 43 m, f/16, ISO 100 | 2.69 m flash distance | 8.82 |
| GN 43 m, f/16, ISO 200 | 3.8 m flash distance | 12.47 |
| GN 43 m, f/16, ISO 400 | 5.38 m flash distance | 17.63 |
| GN 58 m, f/1.4, ISO 100 | 41.43 m flash distance | 135.92 |
| GN 58 m, f/1.4, ISO 200 | 58.59 m flash distance | 192.22 |
| GN 58 m, f/1.4, ISO 400 | 82.86 m flash distance | 271.84 |
| GN 58 m, f/2, ISO 100 | 29 m flash distance | 95.14 |
| GN 58 m, f/2, ISO 200 | 41.01 m flash distance | 134.55 |
| GN 58 m, f/2, ISO 400 | 58 m flash distance | 190.29 |
| GN 58 m, f/2.8, ISO 100 | 20.71 m flash distance | 67.96 |
| GN 58 m, f/2.8, ISO 200 | 29.29 m flash distance | 96.11 |
| GN 58 m, f/2.8, ISO 400 | 41.43 m flash distance | 135.92 |
| GN 58 m, f/4, ISO 100 | 14.5 m flash distance | 47.57 |
| GN 58 m, f/4, ISO 200 | 20.51 m flash distance | 67.28 |
| GN 58 m, f/4, ISO 400 | 29 m flash distance | 95.14 |
| GN 58 m, f/5.6, ISO 100 | 10.36 m flash distance | 33.98 |
| GN 58 m, f/5.6, ISO 200 | 14.65 m flash distance | 48.06 |
| GN 58 m, f/5.6, ISO 400 | 20.71 m flash distance | 67.96 |
| GN 58 m, f/8, ISO 100 | 7.25 m flash distance | 23.79 |
| GN 58 m, f/8, ISO 200 | 10.25 m flash distance | 33.64 |
| GN 58 m, f/8, ISO 400 | 14.5 m flash distance | 47.57 |
| GN 58 m, f/11, ISO 100 | 5.27 m flash distance | 17.3 |
| GN 58 m, f/11, ISO 200 | 7.46 m flash distance | 24.46 |
| GN 58 m, f/11, ISO 400 | 10.55 m flash distance | 34.6 |
| GN 58 m, f/16, ISO 100 | 3.63 m flash distance | 11.89 |
| GN 58 m, f/16, ISO 200 | 5.13 m flash distance | 16.82 |
| GN 58 m, f/16, ISO 400 | 7.25 m flash distance | 23.79 |
Frequently Asked Questions
Common questions about Flash Guide Number Distance Calculator, formulas, and typical use cases.
How do you calculate flash distance from guide number?
At ISO 100, divide guide number by aperture. For other ISO settings, multiply guide number by the square root of ISO/100 before dividing by aperture.
What does a flash guide number mean?
Guide number indicates flash power for manual exposure planning. A higher guide number generally means the flash can illuminate a subject farther away at the same aperture and ISO.
Why does ISO change effective guide number?
Increasing ISO makes the sensor more sensitive, so the same flash output can expose subjects at a greater distance. The relationship scales with the square root of ISO.
Does this replace test shots and light metering?
No. It is a fast starting estimate for manual flash setup. Modifiers, bounce, zoom head settings, and real scene conditions can change the final exposure.
Methodology and Review
This page combines a live calculator, precomputed reference values, and FAQ content from the same conversion definition to reduce mismatch between calculator output and lookup tables.
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For compliance-sensitive work, verify final values against project requirements, governing standards, and manufacturer documentation.