Convert knots to feet per second or feet per second to knots, with m/s, mph, and km/h equivalents for quick comparisons in one calculator.
Knots to ft/s Formula
- knots: speed in nautical miles per hour (kt)
- ft/s: speed in feet per second
- 1.68781: rounded conversion factor; the exact factor is 1852 / (3600 × 0.3048) = 11575/6858
The factor uses the international nautical mile (1852 m exactly) and the international foot (0.3048 m exactly). For quick mental math, multiply knots by 1.69, or just by 1.7 for a rough estimate.
Reference Tables
Common knot values converted to ft/s, m/s, and mph.
| Knots | ft/s | m/s | mph |
|---|---|---|---|
| 1 | 1.69 | 0.51 | 1.15 |
| 5 | 8.44 | 2.57 | 5.75 |
| 10 | 16.88 | 5.14 | 11.51 |
| 15 | 25.32 | 7.72 | 17.26 |
| 20 | 33.76 | 10.29 | 23.02 |
| 30 | 50.63 | 15.43 | 34.52 |
| 50 | 84.39 | 25.72 | 57.54 |
| 100 | 168.78 | 51.44 | 115.08 |
| 250 | 421.95 | 128.61 | 287.69 |
| 500 | 843.90 | 257.22 | 575.39 |
Where these speeds typically show up.
| Range | Context |
|---|---|
| 1 to 6 kt | Light wind, slow current, harbor maneuvering |
| 7 to 25 kt | Sailing wind, cruising small boats, light aircraft taxi |
| 25 to 60 kt | Powerboat cruise, gale to storm wind, light aircraft approach |
| 60 to 250 kt | General aviation cruise to regional jets |
| 250 to 600 kt | Airliner cruise speeds |
Example and FAQ
Example: Convert 22 knots to ft/s.
22 × 11575/6858 ≈ 37.13 ft/s.
Why 1.68781? One international nautical mile is exactly 1852 m, or approximately 6076.1155 international feet. Dividing by 3600 s gives approximately 1.68781 ft/s per knot.
Is a knot the same as 1 mph? No. 1 knot equals about 1.151 mph because a nautical mile is longer than a statute mile.
Quick estimate without a calculator? Multiply knots by 1.7. For 30 kt, that gives 51 ft/s, close to the value of 50.63 ft/s rounded to two decimals.
Going the other way? Divide ft/s by 1.68781. So 50 ft/s × 6858/11575 ≈ 29.6 kt.
