Speed Distance Time Calculator
Calculate speed, distance, or time from any two known values.
Works for any mode of transport — sailing, driving, cycling, running.
The speed-distance-time triangle is the most fundamental relationship in navigation. Any two values give you the third:
The three formulas:
- Speed = Distance / Time
- Distance = Speed × Time
- Time = Distance / Speed
Units matter: Keep speed, distance, and time in consistent units. This calculator accepts any common unit and converts automatically.
Common unit conversions:
- 1 knot = 1.852 km/h = 1.151 mph
- 1 nautical mile = 1.852 km = 1.151 statute miles
- 1 statute mile = 1.609 km
- 1 km = 0.621 miles = 0.540 nautical miles
Worked examples:
Example 1, how long will it take? A sailboat at 5 knots needs to cover 25 nautical miles. Time = 25 / 5 = 5 hours
Example 2, how far did I travel? A hiker walks at 4 km/h for 3 hours 30 minutes. Distance = 4 × 3.5 = 14 km
Example 3, what speed am I doing? A car covers 280 km in 2 hours 20 minutes. Speed = 280 / 2.333 = 120 km/h
Rule of 60: A useful mental shortcut. At 60 knots, you travel 1 nautical mile per minute. At 30 knots, 0.5 nm/min. At 6 knots, 0.1 nm/min (6 nm/hr).
Round-trip average speed is not the arithmetic mean. A common trap. If you drive somewhere at 60 km/h and return at 30 km/h, your average speed is not (60+30)/2 = 45 km/h. It is the harmonic mean:
average speed = 2 × v₁ × v₂ / (v₁ + v₂)
For 60 and 30 km/h: 2 × 60 × 30 / 90 = 40 km/h, not 45. The reason is that you spend more time on the slow leg than the fast leg, so the slow speed weighs more heavily. The arithmetic mean would be correct only if you spent equal time (not equal distance) at each speed. This trips up car testers, pilots calculating fuel reserves, and anyone planning a round-trip ETA.