Calculate speed, distance or time — enter any two values to find the third.
Enter any two values to calculate the third.
The relationship between speed, distance, and time is one of the most fundamental in physics and everyday life. The three formulas are: Speed = Distance / Time, Distance = Speed × Time, Time = Distance / Speed. Know any two of these values and our Speed Distance and time Calculator instantly calculates the third.
This works the same way whether you're comparing everyday transport, like the speed of a bus versus an aircraft over the same distance, or any other scenario where two of the three values are already known.Average speed = Total Distance / Total Time. It is what our calculator computes and what is most useful for travel planning. Instantaneous speed is your speed at one specific moment — what your speedometer shows. Note that average speed is NOT simply the average of two speeds when different times are spent at each speed. For example, driving 60 km/h for 1 hour then 120 km/h for 1 hour gives average speed = 180km / 2h = 90 km/h, not (60+120)/2 = 90 km/h (coincidentally the same here, but not always).
Estimate travel time for road trips by dividing distance by average speed. Calculate fuel consumption by knowing travel time and speed. Determine running pace — converting between minutes per kilometer and km/h. Plan flight routes — commercial aircraft cruise at about 900 km/h. Calculate train journey time for various train types around the world, from regional trains to high-speed rail.
For context: Walking pace ≈ 5 km/h. Cycling ≈ 15-25 km/h. Typical highway speed limits worldwide ≈ 80-130 km/h, varying by country. High-speed rail top speeds ≈ 250-350 km/h in countries that operate them. Commercial aircraft ≈ 900 km/h. Speed of sound ≈ 1,235 km/h. Speed of light = 1,079,252,848 km/h (approximately 3 × 10⁸ m/s). Our speed calculator works for any of these scenarios, anywhere in the world.
The fundamental relationship — distance equals speed multiplied by time — can be rearranged to solve for any of the three variables when the other two are known, making it one of the most practically useful formulas for everyday trip planning. Knowing distance and desired arrival time lets you calculate the required average speed; knowing distance and average speed lets you calculate expected travel time; knowing speed and available time lets you calculate how far you can realistically travel.
Real-world trip time estimates need to account for the fact that average speed over an entire journey is typically lower than a vehicle's maximum or cruising speed, due to traffic, stops, intersections, and varying road types along the route, which is why simple distance-divided-by-speed-limit calculations tend to underestimate actual travel time for anything beyond a short highway stretch.
The most common error in speed-distance-time calculations is mixing units — calculating with distance in miles but speed in kilometers per hour, for example, produces a meaningless result unless units are converted to match first. Always confirming that distance, speed, and time units are consistent with each other (all metric or all imperial, and matching time units like hours vs. minutes) before calculating avoids the single most frequent source of error in this type of calculation.
The basic formula is: Speed = Distance / Time, Distance = Speed × Time, Time = Distance / Speed. These three are always related.
To convert km/h to m/s, divide by 3.6. For example, 90 km/h = 90 / 3.6 = 25 m/s.
Average speed = Total Distance / Total Time. It is not simply the average of two speeds if the time spent at each speed differs.
Travel Time = Distance / Speed. For example, a 300 km journey at 60 km/h takes 300/60 = 5 hours.
