# Speed, distance and time calculator: how to find speed, distance or travel time, and why average speed is not a simple average

> Speed, distance and time are linked by one formula, and knowing any two gives the third. This guide shows how to solve each case, how to convert km/h to metres per second, and why a trip at two speeds does not average to the middle value.

Published 2026-10-09 by Toolcloak. 3 minute read. Original: https://toolcloak.pages.dev/articles/speed-distance-time-calculator-how-to-find-speed-distance-or-travel-time-and-why-average-speed-is-not-a-simple-average
Related free tool: [Speed, Distance & Time Calculator](https://toolcloak.pages.dev/tools/speed-distance-time-calculator)

**Speed**, **distance** and **time** are three views of the same thing: how far you go, how long it takes, and how fast you move. Know any two and you can find the third. The formulas are short, but the units and the idea of average speed trip people up, especially when a journey is made at different speeds.

> **In short**
> - **Speed = distance ÷ time.** **Distance = speed × time.** **Time = distance ÷ speed.**
> - A trip of **150 km** at **60 km/h** takes **2.5 hours**, which is **2 h 30 min**.
> - Speed in km/h ÷ 3.6 gives metres per second, so 60 km/h is **16.67 m/s**.
> - Going 60 km at 60 km/h and coming back at 40 km/h is an average of **48 km/h**, not 50.

## The three formulas

**Example: how long does 150 km take at 60 km/h?**

1. **Write down what you know.** Distance = 150 km, speed = 60 km/h.
2. **Choose the formula.** Time = distance ÷ speed.
3. **Divide.** 150 ÷ 60 = **2.5 hours**.
4. **Convert to hours and minutes.** 0.5 hour is 30 minutes, so the trip takes **2 h 30 min**.

*Choose what to find, fill in the other two values and press Solve. The tool shows time in hours and minutes as well as decimal hours.*

Try it: [Speed, Distance & Time Calculator](https://toolcloak.pages.dev/tools/speed-distance-time-calculator). Pick what you want to find, enter the other two values, and get speed, distance or time.

## Keep the units matching

The tool uses kilometres, hours and km/h. If your numbers are in other units, convert first. Minutes must become hours: 90 minutes is 1.5 hours, not 90. Metres must become kilometres: 2,500 m is 2.5 km. Mixing km with minutes is the most common reason an answer is off by a factor of 60.

- **km/h to m/s:** divide by 3.6. **m/s to km/h:** multiply by 3.6.
- **Minutes to hours:** divide by 60. **Hours to minutes:** multiply by 60.
- **Metres to km:** divide by 1,000.

## Travel time at different speeds

| Speed | Time for 150 km | Speed in metres per second |
| --- | --- | --- |
| 40 km/h | 3 h 45 min | 11.11 m/s |
| 50 km/h | 3 h 0 min | 13.89 m/s |
| 60 km/h | 2 h 30 min | 16.67 m/s |
| 75 km/h | 2 h 0 min | 20.83 m/s |
| 90 km/h | 1 h 40 min | 25.00 m/s |

*The same 150 km. Doubling the speed halves the time, but going from 40 to 60 km/h saves more minutes than going from 75 to 90.*

**Minutes needed for 150 km at different speeds**

|  | Minutes |
| --- | --- |
| 40 km/h | 225 min |
| 50 km/h | 180 min |
| 60 km/h | 150 min |
| 75 km/h | 120 min |
| 90 km/h | 100 min |

*Extra speed gives smaller and smaller savings. Going from 40 to 60 km/h saves 75 minutes here, while going from 75 to 90 km/h saves only 20.*

## Average speed is not a simple average

Suppose you drive 60 km to a town at 60 km/h and return at 40 km/h. The simple average of the two speeds is 50, but the real average speed is **total distance ÷ total time**. The way there takes 1 hour and the way back takes 1.5 hours. The total is 120 km in 2.5 hours, which is **48 km/h**. You spend longer at the slower speed, so it pulls the average down.

**Same trip, two ways of averaging**

| Simple average | Total distance ÷ total time |
| --- | --- |
| 50 km/h | 48 km/h |
| (60 + 40) ÷ 2 | 120 km ÷ 2.5 h |
| Ignores the time spent at each speed | Counts the longer time at 40 km/h |
| Would give 2 h 24 min for 120 km | Gives 2 h 30 min for 120 km |

*Always add the distances and add the times first, then divide.*

> **The tool does not add stops:** The result is time on the move. Fuel stops, traffic, tolls and rest breaks add to the real journey, so add a buffer when planning. A flat extra 10% is a common rough allowance on long drives.

## Solving each case

1. **Decide what is missing:** speed, distance or time.
2. **Check the units** and convert minutes, metres or m/s first.
3. **Use the matching formula** or choose that option in the calculator.
4. **For a journey in parts,** work out distance and time for each part, add them up, then find the average speed.
5. **Add a buffer** for stops and traffic when you plan the real trip.

## Frequently asked questions

### How do I calculate travel time?

Divide the distance by the speed. For 150 km at 60 km/h, the time is 150 ÷ 60 = 2.5 hours, which is 2 hours 30 minutes.

### How do I calculate speed from distance and time?

Divide the distance by the time in hours. A 90 km trip in 1.5 hours means a speed of 60 km/h.

### How do I convert km/h to m/s?

Divide by 3.6. Sixty km/h is 60 ÷ 3.6 = 16.67 metres per second. To go back, multiply metres per second by 3.6.

### What is average speed?

Average speed is total distance divided by total time. It is not the average of the speeds, unless you spend equal time at each speed.

### Why is the average of 60 and 40 km/h not 50?

Because over equal distances you spend more time at the slower speed. The trip takes 1 hour plus 1.5 hours, so 120 km in 2.5 hours is an average of 48 km/h.

### Does the calculator work for miles?

The fields are in km, km/h and hours. For miles and mph the formulas are the same, so enter the numbers in miles and mph and read the answer as miles and mph. The metres-per-second line would then not apply. The [Speed Converter](https://toolcloak.pages.dev/tools/speed-converter) changes between units.