Introduction
Speed is how fast something moves over a certain distance in a given amount of time. In physics, the basic speed formula is simple: Speed = Distance ÷ Time. If you know any two of these three values, you can always find the third. This rule applies whether you're timing a car on the highway, a runner on a track, or a planet moving through space.
This speed calculator lets you solve for speed, distance, or time instantly. Just pick what you want to find, enter the two values you already know, and hit calculate. The tool supports a wide range of units, from meters per second and miles per hour to knots and even the speed of light, so it works for everyday problems and advanced physics alike. It also converts your result into other common speed units automatically, saving you extra steps.
Need to figure out your running pace? Switch to the Pace Calculator tab to find your minutes per mile or per kilometer, complete with split times for popular race distances like 5K, 10K, half marathons, and marathons. There's also a dedicated Speed Converter tab where you can type in any speed value and see it converted across all supported units at once.
How to Use Our Speed Calculator
Enter your known values for distance, speed, or time, and this calculator will solve for the missing value. It also includes a pace calculator for runners and a speed unit converter.
Solve For: Choose whether you want to calculate speed, distance, or time. The calculator will rearrange the formula automatically and mark the output field for you.
Distance: Enter the distance traveled as a number and pick your unit. You can choose from metric units like meters and kilometers, imperial units like miles and feet, or special units like nautical miles and light years.
Speed: Enter the speed value and select your unit. Options range from common units like km/h, mph, and m/s to less common ones like yards per second, inches per minute, or even the speed of light.
Time: Enter the time using one of three input modes. Use the Hours, Minutes, and Seconds fields for simple entry. Use the hh:mm:ss mode to type time with colons, periods, or dashes as separators. Or use the Single Value mode to enter time in one unit such as seconds, minutes, hours, days, or years.
Pace Calculator: Switch to the Pace tab to find your running or walking pace. Choose to solve for pace, distance, or total time. Enter your distance or pick a common race distance like a 5K, 10K, half marathon, or marathon. The calculator shows your pace per kilometer or mile, your speed in km/h and mph, and a full split time table.
Speed Converter: Switch to the Speed Converter tab to convert any speed value into all supported units at once. Enter a number, pick the starting unit, and click Convert to see results for every speed unit available, including m/s, km/h, mph, knots, ft/s, and the speed of light.
What Is Speed?
Speed is how fast something moves. It tells you the distance an object covers in a certain amount of time. For example, if a car drives 100 kilometers in 2 hours, its speed is 50 kilometers per hour (km/h). Speed is one of the most basic and important ideas in physics and everyday life.
The Speed Formula
The formula for speed is simple:
Speed = Distance ÷ Time
This formula connects three values: speed, distance, and time. If you know any two of them, you can always find the third. To find distance, you multiply speed by time. To find time, you divide distance by speed. These three rearrangements of the same formula are all you need for most speed calculations.
Speed vs. Velocity
Speed and velocity sound alike, but they are not the same thing. Speed is a scalar quantity, which means it only has a size (magnitude). It tells you how fast something is going, but not which direction. Velocity is a vector quantity, meaning it includes both how fast and in what direction. A car going 60 mph north has a velocity. A car going 60 mph with no direction stated has a speed. This calculator works with speed, not velocity.
Common Units of Speed
Speed can be measured in many different units depending on the situation:
- km/h (kilometers per hour) – Used in most countries for road speed limits and car travel.
- mph (miles per hour) – Used in the United States and United Kingdom for road speeds.
- m/s (meters per second) – The standard unit in science and physics. It is part of the International System of Units (SI).
- knots – Used in aviation and sailing. One knot equals one nautical mile per hour.
- ft/s (feet per second) – Sometimes used in engineering and ballistics.
- c (speed of light) – Used in astronomy and particle physics. Light travels at about 299,792,458 meters per second in a vacuum.
How to Convert Between Speed Units
Converting between speed units is straightforward when you know the relationship between the distance and time units involved. Here are some common conversions:
- 1 km/h = 0.27778 m/s
- 1 mph = 1.60934 km/h
- 1 knot = 1.852 km/h
- 1 m/s = 3.6 km/h
- 1 ft/s = 0.3048 m/s
To convert, you first change the speed into a base unit like m/s, then convert from m/s into your target unit.
What Is Pace?
Pace is the flip side of speed. Instead of telling you how much distance you cover per unit of time, pace tells you how much time it takes to cover one unit of distance. Runners and walkers use pace more often than speed because it is easier to plan workouts and races with it. Pace is usually expressed as minutes per kilometer (min/km) or minutes per mile (min/mi).
For example, if you run 5 kilometers in 25 minutes, your pace is 5 minutes per kilometer. To convert between pace and speed, you simply divide: if your pace is 5 min/km, your speed is 60 ÷ 5 = 12 km/h.
Average Speed vs. Instantaneous Speed
When you use the formula Speed = Distance ÷ Time, you are calculating average speed. This is the total distance divided by the total time, and it smooths out any changes in speed during the trip. A car might speed up, slow down, and stop at red lights, but its average speed only looks at the big picture.
Instantaneous speed is how fast something is moving at one exact moment. The speedometer in a car shows instantaneous speed. In physics, instantaneous speed is found using calculus by looking at an extremely small interval of time. The change in speed over time is called acceleration.
Real-World Examples of Speed
- Walking: About 5 km/h (3.1 mph)
- Cycling: About 15–25 km/h (9–16 mph)
- City driving: About 50 km/h (31 mph)
- Highway driving: About 100–120 km/h (62–75 mph)
- Commercial airplane: About 900 km/h (560 mph)
- Sound in air: About 343 m/s (1,235 km/h)
- Light in a vacuum: 299,792,458 m/s (about 1.08 billion km/h)
Related Physics Concepts
Speed is closely connected to several other fundamental physics quantities. Once you know an object's speed, you can explore related calculations:
- Kinetic Energy: The energy an object has due to its motion depends on both mass and speed.
- Momentum: The product of mass and velocity is an object's momentum.
- Force: Newton's second law relates force to mass and acceleration.
- Projectile Motion: Objects launched at an angle follow a curved path determined by their initial speed and angle.
- Free Fall: Objects falling under gravity accelerate at a constant rate.
- Horsepower: Vehicle performance often relates speed to engine power.
Tips for Using This Calculator
This speed calculator has three modes. The Speed / Distance / Time tab lets you pick which value to solve for and enter the other two. The Pace Calculator tab is designed for runners and walkers who want to figure out their pace, finish time, or distance. The Speed Converter tab lets you type in a speed and instantly see it in dozens of different units. Make sure you select the correct units for your inputs so your results are accurate.