Speed Calculator Online Free Tool
Speed Calculator
Speed Formula
distance = speed × time
time = distance / speed
Calculate Speed, Distance, or Time
Speed Converter
Speed Comparison Examples
Examples of Different Speeds
| Type | m/s | km/h | mph |
|---|---|---|---|
| Walking | 1.4 | 5 | 3.1 |
| Running | 12.42 | 44.7 | 27.8 |
| Cheetah | 33.53 | 120.7 | 75 |
| Car (avg) | 27.78 | 100 | 62.1 |
| Airplane | 250 | 900 | 559 |
| Sound | 343 | 1235 | 768 |
Speed, distance, and time are related by a fundamental formula used in every field from driving to physics. Knowing any two values, this calculator finds the third. Solve for speed (how fast), distance (how far), or time (how long) and convert between mph, km/h, m/s, and knots instantly. Whether you are planning a road trip, analyzing athletic performance, or solving a physics problem, the speed-distance-time relationship is one of the most useful equations you can master.
Speed, Distance, and Time Formula
The relationship between speed, distance, and time is one of the most fundamental equations in everyday life and physics. It applies equally to a car on a highway, a runner on a track, light traveling through space, and sound moving through air. The key is keeping units consistent: if speed is in miles per hour, distance must be in miles and time in hours.
Speed = Distance / Time Distance = Speed × Time Time = Distance / Speed Unit conversions: 1 mph = 1.609 km/h = 0.447 m/s 1 km/h = 0.621 mph = 0.278 m/s 1 knot = 1.151 mph = 1.852 km/h
Example: Drive 150 miles in 2.5 hours. Speed = 150/2.5 = 60 mph. Or: How long to drive 300 miles at 65 mph? Time = 300/65 = 4.62 hours = 4 hours 37 minutes.
Common Speed References
Having a sense of typical speeds helps you quickly check whether an answer is reasonable. The speed of light (670 million mph) and sound (767 mph at sea level) are useful reference anchors for extreme ends of the scale.
| Mode of Travel | Typical Speed (mph) | Typical Speed (km/h) |
|---|---|---|
| Walking | 3-4 mph | 5-6 km/h |
| Running (recreational) | 5-8 mph | 8-13 km/h |
| Cycling | 10-15 mph | 16-24 km/h |
| City driving | 25-35 mph | 40-56 km/h |
| Highway driving (US) | 55-75 mph | 88-120 km/h |
| High-speed train | 150-200 mph | 240-320 km/h |
| Commercial airplane | 500-600 mph | 800-965 km/h |
| Sound (sea level) | 767 mph | 1,235 km/h |
Average Speed vs Instantaneous Speed
Average speed is total distance divided by total time, including any stops. Instantaneous speed is how fast you are moving at a specific moment, as shown on a speedometer. For a road trip with stops, your average speed is lower than your moving average speed. In physics, instantaneous speed is the derivative of distance with respect to time — the slope of the distance-time graph at any given point.
Average speed = Total Distance / Total Time (including stops) Moving average = Total Distance / Time Actually Moving Example: 300-mile trip, 5 hours total, 45-min stop Average speed = 300/5 = 60 mph Moving average = 300/4.25 ≈ 70.6 mph
Travel Time Planning
When estimating road trip arrival times, average speed calculations often underestimate actual travel time. Traffic, stops, construction, and speed limit changes all reduce your effective average speed. A practical rule of thumb: for trips over 200 miles, assume an effective average speed of 45-55 mph including fuel, food, and rest stops, even on mostly-highway routes.
Frequently Asked Questions
How do I calculate my average speed for a road trip?⌄
Divide total distance by total elapsed time from departure to arrival, including all stops. For a 400-mile trip completed in 7 hours total (including 1 hour of stops), average speed = 400/7 ≈ 57 mph. If you only want your moving average (the speed you were actually traveling), divide by driving time only: 400/6 ≈ 67 mph. GPS and mapping apps typically show moving average speed by default, not total average including stops.
How do I convert mph to km/h?⌄
Multiply mph by 1.60934 to get km/h. To convert km/h to mph, multiply by 0.62137. Quick mental approximation: multiply mph by 1.6 for km/h (slightly under the true value), or divide km/h by 1.6 for mph. Example: 60 mph × 1.6 = 96 km/h (exact: 96.56 km/h). Speed limit reference: 100 km/h ≈ 62 mph, 130 km/h ≈ 81 mph (common European motorway limits).
What is the difference between speed and velocity?⌄
Speed is a scalar quantity (magnitude only: how fast). Velocity is a vector quantity (magnitude and direction: how fast and which way). A car traveling 60 mph north and a car traveling 60 mph south have the same speed but opposite velocities. This distinction matters in physics when calculating momentum, force, and relative motion. In everyday driving contexts, speed and the magnitude of velocity are the same thing.
How does GPS calculate speed?⌄
GPS determines speed by measuring the change in calculated position between consecutive satellite readings and dividing by the time interval. Modern GPS receivers update 1-10 times per second. For more accurate instantaneous speed measurement, some GPS units use the Doppler shift of satellite signals, which detects your motion relative to satellites directly and is more accurate than position-difference methods at low speeds or when stationary.
What is terminal velocity?⌄
Terminal velocity is the maximum speed a falling object reaches when the drag force from air resistance equals the gravitational force. At terminal velocity, acceleration stops and the object falls at constant speed. For a skydiver in a spread-eagle position, terminal velocity is about 120 mph (195 km/h). In a head-down dive position, it can reach 180 mph. A skydiver opening a parachute drops terminal velocity to about 12 mph for a safe landing.