Speed Calculator
Give the speed calculator any two of speed, distance and time and it finds the third, in miles, kilometers, meters, feet or nautical miles, and converts the answer to every common unit.
Speed
- Speed speed = distance / time = 150 mi / 2.5 h.
- 60 mph
- Time as a clock reading 2.5 hours = 150 minutes = 9,000 seconds.
- 2:30:00
- Distance 241,402 meters.
- 150 mi = 241.402 km
- Pace Minutes and seconds to cover one mile or one kilometer: the reciprocal of speed, as runners and walkers use it.
- 1:00 per mile, 0:37 per km
| Unit | Speed |
|---|---|
| miles per hour (mph) | 60 |
| kilometers per hour (km/h) | 96.5606 |
| meters per second (m/s) | 26.8224 |
| feet per second (ft/s) | 88 |
| knots (kn) | 52.1386 |
- The answer is an average speed: the same distance and time at a steady speed. Stops and slowdowns are inside the time, so the speedometer was above this figure some of the way.
How the Speed Calculator works
Speed is distance divided by time. The speed calculator rearranges that one formula three ways: speed = distance / time, distance = speed × time, and time = distance / speed. The default trip is 150 miles in 2 hours 30 minutes. Two and a half hours is 2.5 hours, and 150 / 2.5 = 60 mph.
A speed distance time triangle is the classroom way to remember the rearrangements. Write D on top and S and T side by side underneath. Cover the one you want: D is S × T, S is D over T, and T is D over S.
Units have to match. The formula only works when the units agree: miles with hours give miles per hour, kilometers with hours give km/h, meters with seconds give m/s. The slip that causes most wrong answers is the time. 2 hours 30 minutes is 2.5 hours, not 2.3, and 45 minutes is 0.75 hours. The calculator takes hours, minutes and seconds in separate boxes and converts everything through meters and seconds, so any combination of units works.
Converting speeds. A mile is exactly 1,609.344 meters, so 1 mph is 1.609344 km/h, and 60 mph is 96.56064 km/h. One meter per second is exactly 3.6 km/h. A knot is one nautical mile, 1,852 meters, per hour, which is about 1.15078 mph. The table under every answer gives the speed in all five units.
Average speed is total distance over total time. It is not the average of the speeds. Drive 60 miles at 30 mph and 60 miles back at 60 mph, and the trip takes 2 hours plus 1 hour: 120 miles in 3 hours is 40 mph, not 45. The slow leg lasts longer, so it counts for more. When the legs cover equal distances, the right average is the harmonic mean of the speeds. When they last equal times, the plain average is right.
Time from distance and speed. The answer often comes out as decimal hours, and the calculator turns it into hours and minutes. At 65 mph, 300 miles takes 300 / 65 = 4.615 hours. The minutes are 0.615 × 60 = 36.9, not 61.5, so the trip is about 4 hours 37 minutes, or 4 h 36 min 55 s to the second.
Used as an average speed calculator, it needs the total distance and the total time, including any stops. The formulas assume an average or constant speed. For a speed that changes at a steady rate, such as a car accelerating or a falling object, the kinematics equations are the ones to use.
Speed Calculator FAQ
What is the formula for speed?
Speed = distance / time. 150 miles in 2.5 hours is 150 / 2.5 = 60 mph. Rearranged, distance = speed × time and time = distance / speed.
How do I calculate time from distance and speed?
Divide the distance by the speed, then turn the decimal part of the hours into minutes by multiplying by 60. 300 miles at 65 mph is 4.615 hours, and 0.615 × 60 is about 37 minutes, so 4 hours 37 minutes.
How do I convert mph to km/h?
Multiply by 1.609344, because a mile is exactly 1,609.344 meters. 60 mph is 96.56 km/h. To go back, divide km/h by 1.609344: 100 km/h is 62.14 mph.
How do I find average speed for a trip with different speeds?
Divide the total distance by the total time. 60 miles at 30 mph and 60 miles at 60 mph take 3 hours for 120 miles, an average of 40 mph. Averaging the two speeds gives 45 mph, which is wrong.