Speed Calculator
Solve for speed, distance or time from the other two, in any common unit, and see pace, travel times and the true average speed of a trip.
Average speed for multiple legs
Leg distances use the distance unit above. The calculator adds every distance and every time, then divides, which is the correct way to average speeds.
This is the average for 150 mi covered in 2 h 30 min, including any slower or faster stretches.
Pace and travel times
Pace is the time per mile or kilometer at this speed, shown as minutes:seconds, then the time to cover longer distances.
| Distance | Time at this speed |
|---|---|
| 10 km | 6 min 13 s |
| Half marathon, 21.0975 km | 13 min 7 s |
| Marathon, 42.195 km | 26 min 13 s |
| 100 km | 1 h 2 min 8 s |
| 100 miles | 1 h 40 min |
| 1,000 km | 10 h 21 min 22 s |
Your calculation
The same steps the calculator runs, with your numbers. Distance goes to meters and time to seconds first.
- Distance in meters: 150 mi × 1,609.344 = 241,401.6 m.
- Time in seconds: 2 × 3,600 + 30 × 60 + 0 = 9,000 s (2.5 h).
- Speed: 241,401.6 m ÷ 9,000 s = 26.8224 m/s.
- Convert: 26.8224 m/s ÷ 0.44704 = 60 mph.
Same speed in other units
Converted with the exact NIST factors. Mach uses the sea level speed of sound at 15 °C, 340.294 m/s.
| Unit | Speed | From m/s |
|---|---|---|
| Feet per second | 88 ft/s | m/s ÷ 0.3048 |
| Knots | 52.14 knots | m/s × 3,600 ÷ 1,852 |
| Mach, sea level at 15 °C | Mach 0.0788 | m/s ÷ 340.294 |
Distance covered over time
How far you travel at this speed in a given time.
| Time | Miles | Kilometers |
|---|---|---|
| 10 s | 0.167 | 0.268 |
| 30 s | 0.5 | 0.805 |
| 5 min | 5 | 8.05 |
| 15 min | 15 | 24.14 |
| 30 min | 30 | 48.28 |
| 2 h | 120 | 193.12 |
| 5 h | 300 | 482.8 |
| 8 h | 480 | 772.49 |
Results assume one constant average speed over the whole distance. Real trips include stops and speed changes, and Mach uses standard sea level air at 15 °C.
How the Speed Calculator Works
This speed calculator works with the three quantities that describe steady motion: distance, time and speed. Enter any two and it solves for the third. Choose Speed to find how fast you traveled, Distance to find how far you will go at a known speed, or Time to find how long a trip will take. It accepts meters, kilometers, feet, yards, miles and nautical miles, and reports speed in m/s, km/h, mph, ft/s, knots or Mach.
Every calculation runs in SI units. The calculator converts the distance to meters and the time to seconds, divides or multiplies, then converts the answer back to the unit you picked. The conversion factors are the exact values published by NIST, so a result in mph and the same result in km/h always agree. The Your calculation card repeats those steps with your own numbers.
The result is an average speed. It tells you the steady speed that would cover the same distance in the same time. A car that averaged 60 mph may have stopped at a light and passed 70 mph on the highway, and the calculator cannot see those changes. It only knows the totals you enter.
Speed, Distance and Time Formulas with Worked Examples
The speed distance time triangle is a memory aid for the three formulas. Write D at the top and S and T side by side underneath. Cover the quantity you want: D leaves S × T, S leaves D over T, and T leaves D over S. All three come from the same equation, so you only need to remember s = d ÷ t and rearrange it.
How to calculate speed
This is the average over the whole race, including the start from the blocks. The top speed during the race was higher, because the first meters are spent accelerating.
Distance formula, d = s × t
Time formula, t = d ÷ s
The units must match before you divide or multiply. If the speed is in km/h, the distance must be in kilometers and the time in hours. Mixing miles with km/h, or minutes with hours, is the most common reason a hand calculation disagrees with a calculator.
Speed Unit Conversion Chart
Each row shows what one unit of speed equals in the other units. The factors for the mile, the foot and the nautical mile are exact by definition: 1 mile = 1,609.344 m, 1 foot = 0.3048 m and 1 nautical mile = 1,852 m. One knot is one nautical mile per hour, or 1,852 m in 3,600 s.
| 1 unit | m/s | km/h | mph | ft/s | knots |
|---|---|---|---|---|---|
| 1 m/s | 1 | 3.6 | 2.236936 | 3.280840 | 1.943844 |
| 1 km/h | 0.277778 | 1 | 0.621371 | 0.911344 | 0.539957 |
| 1 mph | 0.44704 | 1.609344 | 1 | 1.466667 | 0.868976 |
| 1 ft/s | 0.3048 | 1.09728 | 0.681818 | 1 | 0.592484 |
| 1 knot | 0.514444 | 1.852 | 1.150779 | 1.687810 | 1 |
mph to km/h and km/h to mph
To convert mph to km/h, multiply by 1.609344. To convert km/h to mph, divide by 1.609344. To convert km/h to m/s, divide by 3.6, because one kilometer per hour is 1,000 m in 3,600 s. To convert knots to mph, multiply by 1.150779.
| mph | km/h |
|---|---|
| 25 | 40.23 |
| 30 | 48.28 |
| 45 | 72.42 |
| 55 | 88.51 |
| 60 | 96.56 |
| 65 | 104.61 |
| 70 | 112.65 |
| 75 | 120.70 |
| 80 | 128.75 |
| km/h | mph | m/s |
|---|---|---|
| 30 | 18.64 | 8.33 |
| 50 | 31.07 | 13.89 |
| 80 | 49.71 | 22.22 |
| 100 | 62.14 | 27.78 |
| 110 | 68.35 | 30.56 |
| 120 | 74.56 | 33.33 |
| 130 | 80.78 | 36.11 |
How to Calculate Average Speed
Average speed is the total distance divided by the total time. That definition covers every trip, whether it has one leg or ten. The mistake people make is averaging the speeds of the legs instead, which only works when every leg took the same amount of time.
Take a round trip of 120 miles each way. You drive out at 60 mph, which takes 2 hours, and return at 40 mph, which takes 3 hours. The trip covers 240 miles in 5 hours, so the average speed is 48 mph. Averaging 60 and 40 gives 50 mph, which is wrong because you spent more time at the slower speed.
The harmonic mean shortcut applies only when the legs cover equal distances. When the legs last equal times, the plain arithmetic mean is correct. For anything else, add up the distances and the times. The multiple legs option in the calculator does this for up to five legs and shows how far a simple mean of the leg speeds would be off.
How Long Will It Take to Drive? Travel Time and Pace
To find how long it will take to drive a distance, divide the distance by the average speed you expect to hold. The table gives moving times, rounded to the nearest minute, for common trip lengths. Real trips usually take longer because of traffic, fuel stops and slower roads, so enter a realistic average rather than the speed limit.
| Distance | At 55 mph | At 65 mph | At 75 mph |
|---|---|---|---|
| 50 miles | 55 min | 46 min | 40 min |
| 100 miles | 1 h 49 min | 1 h 32 min | 1 h 20 min |
| 250 miles | 4 h 33 min | 3 h 51 min | 3 h 20 min |
| 500 miles | 9 h 5 min | 7 h 42 min | 6 h 40 min |
Minutes per mile to mph
Runners and walkers describe speed as pace, the time per mile or per kilometer. Pace is the reciprocal of speed. To convert minutes per mile to mph, divide 60 by the pace in minutes: an 8:00 mile is 60 ÷ 8 = 7.5 mph, and a 7:30 mile is 60 ÷ 7.5 = 8 mph. For metric pace, 60 divided by minutes per kilometer gives km/h, so 5:00 per km is 12 km/h. The calculator shows pace in the first card under the result. For race splits and finish time predictions, the Pace Calculator is built for that job.
Speed vs Velocity, Average vs Instantaneous Speed
In everyday language speed and velocity mean the same thing, but physics separates them. Speed is a scalar: it has a size and no direction. Velocity is a vector: it has both a size and a direction. Average speed is distance traveled divided by time, while average velocity is displacement, the straight line change in position, divided by time.
OpenStax College Physics gives a clear example. Drive 6 km to a store and back home in half an hour and your average speed is 6 ÷ 0.5 = 12 km/h. Your average velocity is zero, because you end where you started. This calculator reports speed, so it uses the distance you actually traveled along the road, not the straight line between start and finish. For the straight line distance between two points or two map coordinates, use the Distance Calculator.
Instantaneous speed is the speed at a single moment, which is what a speedometer displays. Average speed is what you get from total distance and total time, and it is what you need for trip planning. As OpenStax puts it, a speeding ticket is based on the instantaneous value, while working out how long a road trip takes needs the average.
Mach Number, the Speed of Sound and the Speed of Light
The Mach number is a speed divided by the local speed of sound. The speed of sound depends on the gas and its temperature, and NASA gives it as a = √(γRT), where γ is the ratio of specific heats, R is the gas constant for air and T is the absolute temperature. In the standard atmosphere at sea level the temperature is 15 °C (288.15 K), and the result is the value this calculator uses.
Because the speed of sound falls as air gets colder, the same airspeed gives a higher Mach number at cruising altitude than at sea level. Treat the Mach result here as a sea level, 15 °C figure. For a precise Mach number at altitude, compute the speed of sound from the actual air temperature.
The speed of light in a vacuum is exactly 299,792,458 m/s, a value fixed by the definition of the meter. That equals 1,079,252,848.8 km/h, or about 670,616,629 mph. Nothing with mass can reach it, so the calculator stops with an explanation when an entry works out to light speed or faster. That usually points to a units mistake, such as a distance in kilometers entered with a time in seconds intended as hours. The Share of light speed tile shows how far below that limit your result sits.
How to Use the Calculator
- Solve for. Pick speed, distance or time. The box for the quantity you are solving for disappears.
- Distance and unit. Enter the distance traveled and pick its unit. When solving for distance, the unit picks how the answer is shown.
- Time. Enter hours, minutes and seconds. Blank boxes count as zero, and 95 minutes is read as 1 h 35 min.
- Speed and unit. Enter a known speed, or pick the unit for the answer when solving for speed.
- Multiple legs. Open the legs section, tick the box and enter each leg's distance and time in minutes.
Common Mistakes
- Decimal hours. 2 h 30 min is 2.5 h, not 2.3 h. Dividing by 2.3 inflates the speed by about 9 percent.
- Averaging leg speeds. Use total distance over total time instead.
- Mixed units. Kilometers with mph, or seconds with km/h, give answers off by a constant factor.
- Statute and nautical miles. A nautical mile is 1,852 m, about 15 percent longer than a statute mile.
- Mach at altitude. The sea level value overstates the speed of sound in cold air.
Frequently Asked Questions
What is the formula for speed?
Speed equals distance divided by time, written s = d ÷ t. Rearranging the same relationship gives distance as d = s × t and time as t = d ÷ s. The units of the answer come from the units you divide: miles divided by hours gives miles per hour, and meters divided by seconds gives meters per second. For example, 150 miles covered in 2 hours 30 minutes is 150 ÷ 2.5 = 60 mph. Convert minutes to decimal hours, or everything to seconds, before you divide, because 2 hours 30 minutes is 2.5 hours, not 2.3.
How do you calculate average speed?
Divide the total distance by the total time, including every leg of the trip. Do not average the leg speeds unless each leg took the same amount of time. Driving 120 miles out at 60 mph takes 2 hours and returning at 40 mph takes 3 hours, so the average speed is 240 ÷ 5 = 48 mph, not 50 mph. For two legs of equal distance the shortcut is the harmonic mean, 2ab ÷ (a + b): 2 × 60 × 40 ÷ 100 = 48 mph. The multiple legs option in the calculator applies this rule for up to five legs.
How do you convert mph to km/h?
Multiply miles per hour by 1.609344, the exact number of kilometers in one international mile. 60 mph × 1.609344 = 96.56 km/h, and 70 mph is 112.65 km/h. To go the other way, divide km/h by 1.609344, so 100 km/h is 62.14 mph. The factor is exact because the international mile is defined as 1,609.344 meters, which NIST lists in its guide to SI units. For a quick estimate in your head, multiply mph by 1.6 or multiply km/h by 0.62, then use the calculator for the exact value.
How do you convert km/h to m/s?
Divide kilometers per hour by 3.6. One kilometer is 1,000 meters and one hour is 3,600 seconds, so 1 km/h equals 1,000 ÷ 3,600 = 0.2778 m/s. A car at 90 km/h moves 90 ÷ 3.6 = 25 m/s, and 100 km/h is 27.78 m/s. To convert m/s back to km/h, multiply by 3.6: a sprinter averaging 10.44 m/s is moving at 37.58 km/h. Meters per second is the SI unit of speed, so physics problems usually expect answers in m/s.
How long does it take to drive 100 miles?
Divide the distance by your average speed. At 60 mph, 100 miles takes 100 ÷ 60 = 1.667 hours, which is 1 hour 40 minutes. At 55 mph it takes about 1 hour 49 minutes, at 65 mph about 1 hour 32 minutes and at 75 mph exactly 1 hour 20 minutes. These are moving times at a steady average. Traffic, fuel stops and slower road sections lower the real average speed, so a trip planned at the speed limit usually takes longer than the calculation shows. Use the Time option in the calculator to enter your own distance and speed.
What is the difference between speed and velocity?
Speed is a scalar: it tells you how fast something moves, with no direction. Velocity is a vector: it includes both the rate and the direction of motion. Average speed is the total distance traveled divided by time, while average velocity is displacement, the straight line change in position, divided by time. If you drive 6 km to a store and back home in half an hour, your average speed is 12 km/h, but your average velocity is zero because you end where you started. A speedometer shows instantaneous speed, the speed at one moment.
Sources & References
- National Institute of Standards and Technology. NIST Guide to the SI, Appendix B.9: Factors for Units Listed by Kind of Quantity, Special Publication 811 (exact factors for the mile, foot, yard and nautical mile, and for mph, km/h, ft/s and knots). nist.gov
- National Institute of Standards and Technology. CODATA Value: speed of light in vacuum, 2022 CODATA recommended values (299,792,458 m/s, exact). physics.nist.gov
- NASA Glenn Research Center. Speed of Sound Interactive, Beginner's Guide to Aeronautics (a = √(γRT), Mach number definition, about 761 mph at standard sea level). nasa.gov
- NOAA, NASA and U.S. Air Force. U.S. Standard Atmosphere, 1976, NASA TM X 74335 (sea level temperature of 288.15 K and speed of sound of 340.294 m/s). ntrs.nasa.gov
- OpenStax. College Physics 2e, Section 2.3: Time, Velocity, and Speed (speed as a scalar, velocity as a vector, average and instantaneous speed, the 6 km round trip example). openstax.org
- World Athletics. World records set at Berlin World Championships have been ratified, 30 September 2009 (men's 100 m, 9.58 s, Usain Bolt). worldathletics.org
Results are mathematical estimates that assume a constant average speed over the distance entered. They are not a substitute for navigation, flight planning or vehicle instruments. Every number on this page was recomputed with the same formulas the calculator uses. Methodology reviewed: 2026.