Speed, Distance & Time Calculator
Speed, distance or time from the other two — in any units, with the working shown.
Each leg
How it was worked out
About the Speed, Distance & Time Calculator
Work out speed, distance or time when you know the other two, using v = d ÷ t. Every value can be in its own unit — kilometres, miles, nautical miles, metres or feet; km/h, mph, m/s, knots or ft/s — and times can be typed as h:mm:ss, in words (1h 30m) or as a number of seconds, minutes, hours or days.
The answer is shown in the unit you pick and converted to all the others, with the pace (minutes per km and per mile) for walking, running and swimming speeds up to 45 km/h. The working is written out step by step in the units of the answer, so you can check it or copy it into homework.
Average of legs handles a journey in several parts — each with its own distance and either its time or its speed, including stops — and gives the true average speed, total distance ÷ total time.
How to use it
- Choose what to calculate: speed, distance, time, or the average speed of several legs.
- Type the two values you know and pick their units. Times can be
3:30:00,25:00(25 minutes),1h 30mor a plain number in the unit chosen; the line under the box shows how the time was read. - The answer appears in the box you are solving for (marked calculated) and in the dark result panel. Change that box’s unit to see the answer in km/h, mph, knots and so on.
- For a journey in parts, choose Average of legs, give each leg its distance and its time or speed, and add legs as needed. Copy the result with the working, or download the legs as CSV.
Examples
42.195 km in 3:30:00
12.06 km/h (7.491 mph, 3.349 m/s) — a pace of 4:59 per km or 8:01 per mile
350 km at 80 km/h
4.375 h = 4 h 22 min 30 s (4:22:30)
30 knots for 2 hours
60 nautical miles = 111.1 km
10 miles in 45 minutes, answer in km/h
16.09 km ÷ 0.75 h = 21.46 km/h
60 km at 80 km/h, then 40 km at 40 km/h
100 km in 1.75 h = 57.14 km/h — not 60 km/h, the average of the two speeds
1 mile at 30 mph, back at 60 mph
2 miles in 3 minutes = 40 mph
Common uses
- Journey planning: how long a drive, flight or voyage takes at a given speed.
- Running, walking, cycling and swimming: speed and pace from a distance and a finishing time.
- Physics and maths homework on speed, distance and time, with the working.
- Sailing and aviation in knots and nautical miles.
- Checking an average speed over a trip with several stages or stops.
The formulas
- Speed = distance ÷ time:
v = d ÷ t - Distance = speed × time:
d = v × t - Time = distance ÷ speed:
t = d ÷ v - Average speed of a journey in parts = total distance ÷ total time:
v_avg = (d₁ + d₂ + …) ÷ (t₁ + t₂ + …)
The units must match before you divide or multiply: kilometres with hours give km/h, metres with seconds give m/s. The calculator converts everything first and shows that step.
Why the average speed is not the average of the speeds
Average speed is total distance divided by total time, so slower parts of a trip count for longer. Drive 1 mile at 30 mph (2 minutes) and back at 60 mph (1 minute) and you cover 2 miles in 3 minutes: 40 mph, not 45 mph. Only when every leg takes the same time does the simple average of the speeds give the right answer; when every leg is the same distance, the right answer is the harmonic mean.
Units used
Conversion factors are the exact definitions in NIST SP 811: 1 mile = 1,609.344 m, 1 nautical mile = 1,852 m, 1 foot = 0.3048 m, 1 mph = 0.44704 m/s. A knot is one nautical mile per hour (1.852 km/h) and 1 m/s = 3.6 km/h. For conversions only, the speed converter and length converter have every unit.
Sources
- OpenStax, University Physics Volume 1, §3.2 Instantaneous Velocity and Speed — average speed = total distance ÷ elapsed time (Eq. 3.5), and how it differs from average velocity.
- NIST, SP 811 Appendix B.8 — conversion factors (mile, nautical mile, foot, mph).
Limitations
- Speeds are averages over the whole distance; the calculator does not model acceleration (use the SUVAT calculator for that).
- Distance here is the distance travelled along the route, not a straight-line displacement, so this is speed rather than velocity.
- Two-part times such as 25:00 are read as minutes:seconds unless the time unit is set to hours, when 1:30 means 1 h 30 min. Check the line under the time box.
- Distances above about 10 light-years and times above 30,000 years are refused as likely unit mistakes; speeds faster than light are flagged.
Privacy
Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.
Frequently asked questions
How do you calculate speed from distance and time?
Divide the distance by the time: v = d ÷ t. A runner who covers 42.195 km in 3 h 30 min (3.5 h) averages 42.195 ÷ 3.5 = 12.06 km/h. Use matching units — km with hours for km/h, metres with seconds for m/s.
How do I work out how long a journey will take?
Divide the distance by the speed: t = d ÷ v. 350 km at 80 km/h takes 350 ÷ 80 = 4.375 hours. The 0.375 h is 0.375 × 60 = 22.5 minutes, so the journey takes 4 h 22 min 30 s.
Why is my average speed not the average of my two speeds?
Because you spend longer at the slower speed. 60 km at 80 km/h takes 0.75 h and 40 km at 40 km/h takes 1 h, so the whole 100 km takes 1.75 h: 100 ÷ 1.75 = 57.14 km/h, not (80 + 40) ÷ 2 = 60 km/h. Always divide the total distance by the total time.
What is the difference between speed and velocity?
Speed is how fast something moves, without a direction. Velocity includes the direction, and average velocity is the straight-line displacement divided by the time. After a round trip your displacement — and so your average velocity — is zero, but your average speed is not.
How do I convert km/h to m/s?
Divide by 3.6, because 1 km/h = 1,000 m ÷ 3,600 s. So 72 km/h = 20 m/s, and 20 m/s × 3.6 = 72 km/h. For mph, 1 mph = 1.609344 km/h exactly.
How do I enter a time like 1 hour 5 minutes?
Type 1:05:00, or 1h 5m, or pick hours and type 1.0833. With the h:mm:ss unit, a two-part time such as 25:00 means 25 minutes and 0 seconds, like a stopwatch. The line under the box confirms how it was read.