Speed Calculator
Accurately calculate speed, distance, or time. Convert instantly between mph, km/h, m/s, and knots.
Speed, Distance, and Time Formulas
Whether you are calculating the speed of a car, a runner's pace, or solving a physics problem, the relationship between speed, distance, and time is constant. Here are the three fundamental formulas:
1. Speed Formula
Speed determines how fast an object is moving. It is the ratio of distance traveled to the time taken.
Speed = Distance / Time
Example: If a train covers 300 km in 2.5 hours, the average speed is 300 / 2.5 = 120 km/h.
2. Distance Formula
To calculate the total distance covered, you multiply the average speed by the time duration.
Distance = Speed × Time
3. Time Formula
To find out how long a trip will take, divide the distance by the speed.
Time = Distance / Speed
Speed vs. Velocity: What's the Difference?
While often used interchangeably, there is a key difference in physics:
- Speed is a scalar quantity. It only measures magnitude (e.g., "50 mph").
- Velocity is a vector quantity. It measures magnitude AND direction (e.g., "50 mph East").
Common Speed Conversions Reference
Use this table for quick reference between common speed units.
| Miles per Hour (mph) | Kilometers per Hour (km/h) | Meters per Second (m/s) |
|---|---|---|
| 10 mph | 16.09 km/h | 4.47 m/s |
| 20 mph | 32.19 km/h | 8.94 m/s |
| 30 mph | 48.28 km/h | 13.41 m/s |
| 40 mph | 64.37 km/h | 17.88 m/s |
| 50 mph | 80.47 km/h | 22.35 m/s |
| 60 mph | 96.56 km/h | 26.82 m/s |
| 70 mph | 112.65 km/h | 31.29 m/s |
| 100 mph | 160.93 km/h | 44.70 m/s |
Frequently Asked Questions (FAQ)
How do I calculate average speed?
To calculate average speed, divide the total distance traveled by the total time taken. For example, traveling 150 km in 3 hours gives an average speed of 50 km/h.
What is 1 knot in km/h?
1 knot (nautical mile per hour) is equal to exactly 1.852 km/h. It is slightly faster than 1 mile per hour (1.15 mph).
How fast is the speed of sound?
The speed of sound depends on the medium (air, water) and temperature. In dry air at 20°C (68°F), it is 343 meters per second (approx. 1,235 km/h or 767 mph).
Can I calculate speed if I have time in minutes?
Yes, but you must convert minutes to hours if your speed unit is mph or km/h. For example, 30 minutes is 0.5 hours. Our calculator handles this conversion automatically.