Speed, Distance and Time Calculator
This speed distance time calculator finds any of the three: leave the one you want blank. 150 miles in 3 hours is 50 mph, which is about 80.5 km/h or 22.35 m/s. A trip of 100 miles at 50 mph takes exactly 2 hours.
Source: Wikipedia – Speed: average speed, units and conversion (1 m/s = 3.6 km/h). Updated: .
How it is calculated
The speed, distance and time formula
Speed is distance per time: v = s ÷ t. Rearranged, distance is s = v × t and time is t = s ÷ v. For 150 miles in 3 hours, v = 150 ÷ 3 = 50 mph.
How to use the calculator
Enter two of the three values and leave the one you want blank. Give the time in hours, minutes and seconds. The result appears at once, together with the speed in other units and the running pace in minutes per kilometre.
Converting units
- 1 m/s = 3.6 km/h, and 1 km/h = 0.2778 m/s.
- 1 mph (mile per hour) = 1.609344 km/h.
- 1 knot = 1 nautical mile per hour = 1.852 km/h.
Worked examples
| Question | Calculation | Answer |
|---|---|---|
| How long to drive 300 miles at 70 mph? | t = 300 ÷ 70 | 4.29 h = 4 h 17 min |
| How long for 100 km at 80 km/h? | t = 100 ÷ 80 | 1.25 h = 1 h 15 min |
| Speed for 10 km in 50 minutes? | v = 10 ÷ (50 ÷ 60) | 12 km/h (5:00 min/km) |
| Marathon (42.195 km) in 4 hours? | v = 42.195 ÷ 4 | 10.55 km/h (6.55 mph) |
| Distance at 65 mph for 2.5 hours? | s = 65 × 2.5 | 162.5 miles |
The most common mistake: minutes are not decimals
Convert minutes to hours before dividing: 1 h 30 min is 1.5 h, not 1.3 h, and 45 min is 0.75 h. Keep units consistent – miles with mph, kilometres with km/h. To memorise the formulas, picture a triangle with distance on top and speed and time below: cover the value you want and the other two show the operation.
Average speed
Average speed is always total distance divided by total time, not the mean of the individual speeds. Drive 100 km at 50 km/h and 100 km at 100 km/h and you need 2 + 1 = 3 hours for 200 km, an average of 66.7 km/h, not 75.
Related calculators
Convert speeds with km/h to mph, plan a run with the running pace calculator, estimate fuel for a trip with the fuel consumption calculator, and measure your current speed with the GPS speedometer.
Limits
The calculator assumes a constant speed. Acceleration, braking, stops and hills change real times, so the result is an estimate for uniform motion.
Frequently asked questions
How do you calculate speed?
Divide distance by time: v = s ÷ t. 150 miles in 3 hours is 50 mph.
How do I find time from distance and speed?
Divide distance by speed: t = s ÷ v. 100 miles at 50 mph takes 2 hours.
How do I convert m/s to km/h?
Multiply by 3.6. 10 m/s is 36 km/h, and to go back divide km/h by 3.6.
How do you find average speed over two legs?
Total distance divided by total time. Do not average the two speeds, because the slower leg takes more time.
What is a knot?
A knot is one nautical mile per hour, or 1.852 km/h. It is used in shipping and aviation.
How long does it take to drive 300 miles at 70 mph?
300 ÷ 70 = 4.29 hours, which is 4 hours 17 minutes without stops.
How do I use minutes in the speed formula?
Convert them to hours first by dividing by 60. 50 minutes = 0.833 h, so 10 km in 50 minutes is 10 ÷ 0.833 = 12 km/h.
Sources and legal basis
- Wikipedia – Speed: average speed, units and conversion (1 m/s = 3.6 km/h)
- Wikipedia – Nautical mile: 1 knot = 1 nautical mile per hour = 1.852 km/h
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