A speed calculator for trips, runs and voyages
This free speed calculator solves the classic triangle of speed, distance and time: give any two and it finds the third. Distances can be in kilometres, miles, metres or nautical miles and time in hours, minutes and seconds; the answer appears in km/h, mph, m/s and knots together, with your pace per kilometre and per mile.
Add a departure time and any stops to get an arrival time, or switch to average speed over legs for a journey made at different speeds. That mode also explains the most common mistake in speed questions — averaging the speeds instead of dividing total distance by total time.
How to use the Speed Calculator
- Choose Speed, distance, time, then pick what you want to find: speed, distance or time.
- Enter the two known values with their units — for example 240 km and 3 h 0 min 0 s to find a speed.
- Optionally set a departure time and minutes of stops and breaks to see when you will arrive.
- Read the answer, the same speed in four units, the pace and the numbered working.
- For a trip with several parts, switch to Average speed over legs, enter each leg’s distance and its speed or time (h:mm), and add legs as needed.
Speed Calculator features
Any of the three
Find speed, distance or travel time; mismatched units such as miles at km/h are converted for you.
Four speed units at once
km/h, mph, m/s and knots side by side, using exact definitions of the mile and nautical mile.
Arrival time
Departure clock time plus travel time and stops, with am/pm and a “+1 day” flag after midnight.
Pace
Minutes per kilometre and per mile for runners, walkers and cyclists.
Multi-leg average
Mix legs given by speed and by time; the true average and the misleading simple mean are shown side by side.
Speed, distance and time formulas
The three quantities are tied by one relationship: speed = distance ÷ time. Rearranged, distance = speed × time and time = distance ÷ speed. The units must match — a speed in km/h needs a distance in kilometres and a time in hours — so convert before dividing. These are the exact factors the calculator uses:
| Unit | In km/h | Definition |
|---|---|---|
| 1 m/s | 3.6 | 1 metre per second × 3,600 s/h |
| 1 mph | 1.609344 | International mile = 1,609.344 m |
| 1 knot | 1.852 | One nautical mile (1,852 m) per hour |
| 1 km/h | 1 | ≈ 0.621371 mph ≈ 0.539957 knots |
Worked examples
- Find a speed: 240 km in 3 hours is 240 ÷ 3 = 80 km/h, which is 49.71 mph, 22.22 m/s or 43.20 knots.
- Find a travel time and arrival: 300 km at 75 km/h takes 300 ÷ 75 = 4 h. Leave at 08:30, add a 30-minute break, and you arrive at 13:00. Door to door, your average is 300 ÷ 4.5 = 66.67 km/h.
- Find a distance: 60 mph for 2 h 30 min covers 60 × 2.5 = 150 miles (241.402 km).
- A run: 10 km in 50 minutes is 12 km/h, a pace of 5:00 per km or 8:03 per mile. For race splits and finish-time predictions, use the pace calculator.
- At sea or in the air: 1,000 nautical miles at 450 knots takes 1,000 ÷ 450 = 2.222 h = 2 h 13 min 20 s.
Average speed: the round-trip trap
You drive 60 km to a town at 60 km/h and come back the same 60 km at 40 km/h. The average is not (60 + 40) ÷ 2 = 50 km/h. The outward leg takes 1 hour and the return 1.5 hours, so you cover 120 km in 2.5 hours: 48 km/h. The slow leg lasts longer, so it pulls the average down. For equal distances the right answer is the harmonic mean, 2 ÷ (1/60 + 1/40) = 48.
The same rule applies to any multi-part trip: add up all the distances, add up all the times, and divide. To convert a single speed without a journey, use the speed converter; to budget the trip, the fuel cost calculator takes the same distance.
Speed Calculator FAQ
How does a speed calculator work out speed?
It divides the distance by the time taken after putting both in matching units. 150 km in 1 h 40 min is 150 ÷ 1.6667 h = 90 km/h. The speed calculator then shows the same speed in mph, m/s and knots.
How do I calculate travel time?
Divide the distance by your average speed: 450 km at 90 km/h is 5 hours. Add stops separately — that is what the “Stops and breaks” box does for the arrival time.
How do I calculate average speed for a whole journey?
Divide the total distance by the total time, including slower parts. Never average the speeds of the legs unless each leg took the same amount of time.
What is the difference between speed and velocity?
Speed is how fast something moves; velocity also has a direction. For a journey along a road, the calculator’s “speed” is the average speed over the distance travelled.
How do I convert km/h to mph?
Divide by 1.609344 (or multiply by about 0.6214). 100 km/h is 62.14 mph. Knots are km/h ÷ 1.852, and m/s are km/h ÷ 3.6.
Does the arrival time handle time zones?
No — it adds the travel time to your departure clock time. If you cross a time zone, adjust the result with the time zone converter.