Home › Converters › Speed Calculator

Speed Calculator

Calculate speed with our free speed calculator. Enter a distance and a travel time, and it works out your average speed in miles per hour and kilometers per hour — 150 miles in 2.5 hours is 60 mph, or 96.56 km/h.

Common speeds

How it works

Speed is simply distance divided by time. If you cover 150 miles in 2.5 hours, your average speed is 150 ÷ 2.5 = 60 miles per hour. The same idea works for any units: kilometers divided by hours gives kilometers per hour, and meters divided by seconds gives meters per second. The calculator takes your distance and time, divides them, and then shows the answer in both mph and km/h so you can use whichever unit your map or speedometer uses.

The key word is average. A car on a highway rarely holds one steady speed — it speeds up, slows down for traffic, and stops for fuel. Average speed smooths all of that out into a single number: total distance divided by total time. If you want your true door-to-door average, include every stop in the time. If you only count the time you were actually moving, you get your moving average, which will be higher. Both are useful, but they answer different questions, so be clear which one you are calculating.

To convert between mph and km/h, use 1 mile = 1.60934 kilometers. Multiply mph by 1.60934 to get km/h, or divide km/h by 1.60934 to get mph. So 60 mph × 1.60934 = 96.56 km/h, and 100 km/h ÷ 1.60934 = 62.14 mph. Minutes need care too: time must be in hours, so turn minutes into decimals first — 30 minutes is 0.5 hours, 45 minutes is 0.75 hours, and 1 hour 30 minutes is 1.5 hours.

Road trips are the most common use. Before you leave, divide the trip distance by the speed you expect to average, and you have your driving time. A 300-mile drive at an average of 60 mph takes 5 hours; at 50 mph it takes 6 hours, so even a small drop in average speed adds a full hour. Runners use the same math in reverse: pace is time divided by distance, so a 10-minute mile is 6 mph, and a 6-minute mile is 10 mph. Cyclists, delivery drivers, and hikers all use the same formula — only the units change.

Worked example

James is driving from Dallas to Houston, a trip of 150 miles, and he wants to know his average speed if the drive takes 2 hours 30 minutes.

Step 1: Write down the distance — 150 miles.
Step 2: Turn the time into hours — 2 hours 30 minutes = 2.5 hours.
Step 3: Divide: 150 ÷ 2.5 = 60.
Step 4: Read the answer — 60 mph.

That is the exact result this calculator gives for 150 miles in 2.5 hours: 60 mph, which is 96.56 km/h. In the other direction, a 100 km trip covered in 1 hour is 100 km/h, or 62.14 mph — the same speed, just measured in different units. James can now tell his family he will average 60 mph and arrive in about two and a half hours.

FAQ