Knots to MPH Converter
Type knots to get mph. A knot is one nautical mile (1,852 m) per hour, about 15% faster than one mph.
30 kn =
34.5234mph
30 knots is 34.5234 miles per hour.
- 1 kn
- 1.1508 mph
- 1 mph
- 0.869 kn
How to convert knots to mph
A knot is one nautical mile per hour, and a nautical mile is exactly 1,852 meters, against 1,609.344 meters for the statute mile used on land. So mph = knots × 1,852 ÷ 1,609.344, which is knots × 1.15078 to six figures.
A sailboat making 7 knots is moving at 7 × 1.15078 = 8.06 mph. A cruising airliner with an airspeed of 450 knots covers about 517.85 mph through the air, before any tailwind or headwind.
To get km/h instead, multiply knots by 1.852; that factor is exact, since both the nautical mile and the kilometer are fixed in meters.
miles per hour = knots × 1.15078 (rounded)
- The nautical mile (1,852 m) and the knot (1,852 m per hour) are non-SI units accepted for use with the SI in marine and air navigation. Source: BIPM, The International System of Units (SI Brochure, 9th edition).
- On the Beaufort scale, a gale (force 8) starts at 34 knots, about 39 mph, and hurricane force (force 12) at 64 knots, about 74 mph. Source: Met Office, The Beaufort wind force scale.
How to estimate knots to mph in your head
Add 15%: take a tenth, add half of that tenth again, and add the result. For 30 knots: a tenth is 3, half of that is 1.5, so 30 + 4.5 = 34.5 mph, compared with the precise 34.52. The rule is off by less than 0.1%.
For quick weather reading, “knots plus one-seventh” is also close: 21 knots + 3 = 24 mph (true value 24.17).
Knots to mph chart
Wind, boat and aircraft speeds in knots, with miles per hour.
| Knots (kn) | Miles per hour (mph) | What it is |
|---|---|---|
| 1 | 1.1508 | |
| 2 | 2.3016 | |
| 5 | 5.7539 | |
| 7 | 8.0555 | |
| 10 | 11.5078 | a fresh breeze for sailing |
| 12 | 13.8094 | |
| 15 | 17.2617 | |
| 20 | 23.0156 | |
| 25 | 28.7695 | |
| 30 | 34.5234 |
Show all 21 rowsShow fewer
| 34 | 39.1265 | gale force begins |
| 40 | 46.0312 | |
| 48 | 55.2374 | |
| 50 | 57.539 | |
| 64 | 73.6499 | hurricane force begins |
| 80 | 92.0624 | |
| 100 | 115.078 | |
| 150 | 172.617 | |
| 250 | 287.695 | |
| 450 | 517.851 | a typical airliner cruise |
| 500 | 575.39 |
Frequently Asked Questions
Why do ships and planes use knots?
A nautical mile was originally one minute of latitude, so a navigator could measure distances straight off a chart’s latitude scale. Speeds in knots fit that system, and the convention stuck in aviation and at sea.
Is a knot faster than one mph?
Yes. One knot is 1.15078 mph, so any speed in knots is about 15% bigger when written in mph. 100 knots is 115.08 mph.
Should I say “knots per hour”?
No. A knot already means nautical miles per hour, so “knots per hour” would be an acceleration. Just say 20 knots.