Speed Calculator

Speed is distance divided by the time it takes

Speed tells you how far something travels in a given amount of time. Speed = distance ÷ time, and rearranging gives distance = speed × time and time = distance ÷ speed. If you drove 150 miles in 2 hours 30 minutes, 150 ÷ 2.5 = 60, so your speed was 60 mph. Any two of the three values fix the third: pick the value to solve for in the triangle, then fill in the other two fields.

The average speed of a trip made in several legs is not the average of the leg speeds. It is the total distance divided by the total time. Drive out at 60 mph and back at 40 mph over the same route and your average is 48 mph, not 50 mph. Enter the two legs on separate lines in the calculator and it shows that figure straight away.

When you need to calculate speed

You calculate speed to compare recorded trips or to estimate how long something will take. The formula is the same every time, but what you already know changes, so the value you solve for changes too.

• Driving and trip planning: divide the miles left by your usual average speed to estimate arrival time, or divide the miles you covered by the time it took to see your real average.
• Hitting a target average: divide a stretch of road by the average speed you want to hold. A 20-mile stretch at an average of 50 mph takes 20 ÷ 50 = 0.4 h, or 24 minutes, and finishing sooner means your average was higher than 50 mph.
• Running, walking and cycling: turn the distance and time from a fitness app into mph or time per mile so you can compare with earlier efforts.
• Homework and physics problems: convert between m/s, m/min and mph, or find the average speed of a round trip where the way back is faster or slower.

How to use the calculator

1. Choose what to solve for: tap distance, speed or time in the triangle. The highlighted field is the one being calculated, and that column of the table turns into a dashed cell that shows the result.
2. Choose units: pick a distance unit (km, m or miles) and a speed unit (km/h, m/min, m/s or mph). Values you already entered are rewritten in the new unit, so the underlying quantity does not change.
3. Enter the other two values: fill in the two fields that are not being solved for. Enter time in the hour, minute and second fields, or use only the minutes field for something like 90.
4. Split into legs: if speed changes, as on an out-and-back trip, press Add leg. With two or more lines the top result becomes the overall average speed, and the total line shows total distance and total time.
5. Read the pictures: on the distance–time graph the slope of the line is the speed, and the speed ruler below shows how that speed compares with walking, a cheetah and an airliner.
6. Save and share: Copy result copies the formula and sentence, and Copy link copies an address that contains your values. The calculation runs in your browser only and nothing is sent to a server.

The three formulas and the distance–speed–time triangle

One triangle covers all three formulas. Put distance in the top cell and speed and time in the two bottom cells, then cover the value you want. Cover distance and the two bottom cells sit side by side: speed × time. Cover speed and distance sits over time: distance ÷ time. Cover time and you get distance ÷ speed. Read the horizontal line as divide and the vertical line as multiply.

Units must match before you calculate. For miles per hour, use miles and hours. For meters per second, use meters and seconds. One hour 30 minutes is 1.5 hours, and 1 hour 20 minutes is 1.333… hours, so minutes are divided by 60 and added to the hours. The calculator converts distance to meters and time to seconds internally, then shows the result in the units you chose.

Converting between mph, km/h, m/min and m/s

A mile is exactly 1,609.344 m, so 1 mph = 1,609.344 m ÷ 3,600 s = 0.44704 m/s, and mph × 1.609344 gives km/h. To go from km/h to m/s, divide by 3.6, because a kilometer is 1,000 m and an hour is 3,600 s. Meters per minute is km/h × 1,000 ÷ 60. A nautical mile is exactly 1,852 m, and a knot is a speed of one nautical mile per hour.

Runners often think in time per mile, which is speed written upside down. Divide 60 by the minutes one mile takes to get mph. A 10-minute mile is 60 ÷ 10 = 6 mph, and 8 minutes 30 seconds per mile is 60 ÷ 8.5 ≈ 7.06 mph.

Average speed is not the average of the leg speeds

Average speed over several legs is total distance ÷ total time. Adding the leg speeds and dividing by the count is usually wrong, because slow legs take longer and so count for more in the overall figure. Drive 60 miles at 60 mph and return the same 60 miles at 40 mph: the legs take 1 hour and 1 hour 30 minutes, and 120 mi ÷ 2.5 h = 48 mph. That is lower than the plain average of 50 mph.

When both legs cover the same distance, the average speed is 2 × a × b ÷ (a + b), the harmonic mean, and it equals the plain average only when the two legs take the same time. If you spend more time in the faster leg, the true average can even beat the plain average.

The same arithmetic gives the shortest time for a stretch if you want to hold a target average: divide the length of the stretch by that average speed. A 20-mile stretch at 50 mph takes 24 minutes, and speeding up or slowing down inside the stretch does not matter, because the average depends only on total distance and total time.

Speed and velocity are not the same thing

In physics, average speed is the distance traveled divided by the time taken, while average velocity is the change in position from start to finish (the displacement) divided by the time. Run once around a 400 m track in 1 minute 40 seconds and your average speed is 400 ÷ 100 = 4 m/s (about 8.95 mph). You finished where you started, so the displacement is 0 and the average velocity is 0. In everyday talk, “velocity” is often used loosely for speed, but physics keeps direction in velocity. This calculator works with distance traveled, so it gives speed.

Reading the distance–time graph

On a graph with time across and distance up, the slope of the line is the extra distance covered per unit of time, which is the speed. Fast legs are steep, slow legs are shallow, and a stop shows up as a flat line. With two or more legs, the dashed line from the origin to the end point is the overall average speed. It meets the real line at the end because both cover the same total distance in the same total time. The dot moves in proportion to real time, so it lingers longer on slow legs.

How fast is this speed?

The speed ruler puts everything from walking to Earth's orbit on one logarithmic scale, so each major step is a factor of 10. The reference values are in the table below. The sentence under your result says how many times the nearest reference below it your speed is, and what percentage of the nearest reference above it.

Common mistakes

• Entering 1 hour 30 minutes as 1.3 hours: minutes are fractions of 60, not of 100. 1 hour 30 minutes is 1.5 hours, and 1 hour 15 minutes is 1.25 hours. The calculator takes hours, minutes and seconds in separate fields to avoid this.
• Mixing meters and km/h: for 1,500 m in 15 minutes, 1,500 ÷ 0.25 gives 6,000, but that is meters per hour, which is 6 km/h. Put everything in one unit before dividing.
• Averaging the leg speeds: 60 mph out and 40 mph back averages 48 mph, not 50 mph. If you drove the first half of a round trip at 60 mph, no speed on the way back can lift the overall average to 120 mph.
• Recalculating from rounded values: 80 mph written as 35.76 m/s and then multiplied by a time can drift in the last digit. The calculator carries the unrounded value when you switch units or change what to solve for.
• Forgetting stops: dividing by a total that includes a rest stop lowers the average. To include a stop in the average, add it as a leg with a distance of 0 while solving for speed; for the speed while moving, enter only the moving legs.

Limits and cautions

• The speed here is an average that assumes each leg was traveled at one steady pace. It does not draw traffic lights, acceleration or congestion that change the instantaneous speed.
• Speed and distance are shown to two decimals (four significant digits below 1), and time is rounded to whole seconds once it reaches 60 seconds. Rounded values carry a “≈”.
• The walking values are group averages by age and sex, and the cheetah value is a top speed measured during hunting in the wild. The airliner value converts Mach 0.85 using the temperature of the standard atmosphere at 11 km, so it is an estimate and differs from the ground speed of a real flight.
• World records change when new ones are set. The records in the table were checked on the World Athletics list on the date below.
• Legal speed limits and enforcement thresholds are not judged by this calculator. Use the result only as an estimate of average speed.

Basis: unit factors are the defined values in NIST SP 811 Appendix B.8. World records and reference speeds from World Athletics, NASA and the other sources below were checked on October 21, 2026.

Sources

• 01NIST Guide to the SI (SP 811), Appendix B.8 Factors for Units Listed Alphabeticallymile = 1,609.344 m, nautical mile = 1,852 m, knot = 0.514 444 m/s
• 02OpenStax, College Physics 2e, 2.3 Time, Velocity, and SpeedAverage speed = distance traveled ÷ elapsed time, which differs from average velocity (displacement ÷ time)
• 03World Athletics, World RecordsMen's 100 m 9.58 (Usain Bolt, 2009-08-16, Berlin); men's marathon 1:59:30 (Sabastian Sawe, 2026-04-26, London)
• 04Bohannon RW, Andrews AW. Normal walking speed: a descriptive meta-analysis. Physiotherapy. 2011;97(3):182-189Group means from 143.4 cm/s (men in their 40s) to 94.3 cm/s (women aged 80-99)
• 05Wilson AM et al. Locomotion dynamics of hunting in wild cheetahs. Nature. 2013;498:185-189Top speed 25.9 m/s
• 06NASA, Earth Fact SheetMean orbital velocity 29.78 km/s
• 07U.S. Standard Atmosphere, 1976 (NASA-TM-X-74335)Speed of sound computed from 288.15 K at sea level, 216.65 K at 11 km, R* 8.314 32, M0 28.9644 g/mol and γ 1.4
• 08Boeing, Boeing Products (787)Cruise speed Mach 0.85

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