Average Speed Calculator

Solve for Speed, Distance or Time

Average Speed Formula

Formula

\[ v_{\text{avg}} = \frac{D}{t} \]

Where:

\(v_{\text{avg}}\) — average speed (m/s)
\(D\) — total distance travelled, i.e. the full path length (m)
\(t\) — total elapsed time (s), including stops

The formula says that average speed is the total length of the path you actually travelled divided by the total time the trip took. When a trip is entered as segments, two quantities are computed:

\[ v_{\text{avg}} = \frac{\sum |d_i|}{\sum t_i} \quad\text{(average speed, unsigned)}, \qquad \bar{v}_{\text{avg}} = \frac{\sum d_i}{\sum t_i} \quad\text{(average velocity, signed)} \]

Average speed always uses the absolute path lengths, while average velocity uses the net signed displacement, so a segment travelled in the opposite direction reduces it.

Average Speed – Calculation Example

Example: you drive 150 km in 2 hours and want to know your average speed.

\[ v_{\text{avg}} = \frac{D}{t} = \frac{150\ \text{km}}{2\ \text{h}} = 75\ \text{km/h} \]

Converting to SI units to check: \( D = 150{,}000\ \text{m} \), \( t = 7200\ \text{s} \), so

\[ v_{\text{avg}} = \frac{150{,}000}{7200} = 20.833\ \text{m/s} \approx 75\ \text{km/h} \approx 46.6\ \text{mph} \]

Result: the average speed is 75 km/h (20.833 m/s, 46.6 mph).

How to Use the Calculator

Choose the Input mode: "Total distance and total time" if you know the overall figures, or "Multiple segments" if you want to list each leg of the trip separately.
In total mode, enter the Total distance (D), pick its unit (km, m, mi or ft), then enter the Total time (t) with its unit (h, min or s).
In segment mode, first select the Segment distance unit and Segment time unit — they apply to all segments.
Enter the Segment distances separated by spaces, semicolons or new lines. Use a negative value for a leg travelled in the opposite direction (e.g. driving back).
Enter the Segment times — the same number of values, in the same order as the distances. Each time must be greater than zero.
Read the results: average speed (and average velocity in segment mode) in m/s, km/h and mph, plus a per-segment breakdown.

What Is Average Speed?

Average speed describes how fast you covered ground over a whole trip, regardless of how the pace varied along the way. It is a scalar quantity: it has a size but no direction. If you drove 150 km in two hours, your average speed was 75 km/h even if you sometimes moved at 100 km/h and sometimes sat at a red light. Physically, it is the constant speed at which you would have covered the same distance in the same time.

A closely related but distinct quantity is average velocity, which is a vector: it equals the net displacement divided by the elapsed time. Displacement is the straight-line change in position from start to finish, not the path length. If you walk 3 km east and then 3 km west in one hour, your average speed is 6 km/h, but your average velocity is zero because you ended where you started. This calculator shows both quantities when you enter segments, so you can see the difference concretely.

How to interpret the result depends on the question you are asking. For travel planning, fuel estimates and "how long will the trip take" reasoning, average speed is what you need, because it is based on the actual route. Average velocity matters in physics problems involving direction — for example when analysing motion along a line with back-and-forth movement.

Assumptions, Limitations and Tips

Time includes stops. Average speed is based on total elapsed time. If your 2-hour trip included a 20-minute break, that break is part of \( t \). If you want the moving-time average, subtract the stops before entering the time.
Segment mode is one-dimensional. A negative distance means "opposite direction". Trips that turn through angles (not just forward/backward) cannot be fully described by a sign, so only the average speed is meaningful for them.
No time between segments. The calculator assumes each segment's time covers everything that happened during it; gaps between segments are not modelled separately, so include waiting time inside the segment times.
The average is not a maximum. An average speed of 75 km/h tells you nothing about the top speed reached — instantaneous speed can be much higher.
Unit consistency. The calculator converts everything to SI units internally (metres and seconds), so you can mix units freely, e.g. distance in miles and time in minutes.

If you are solving a more detailed motion problem, you may also find the Kinematic Equations Solver and the Displacement Calculator useful. To find how fast you were going at the end of an acceleration phase, see the Final Velocity Calculator, or use the Acceleration Calculator to analyse changes in speed over time.

Frequently Asked Questions

How do I calculate average speed by hand?

Divide the total distance travelled by the total elapsed time: \( v_{\text{avg}} = \frac{D}{t} \). For example, 240 km in 3 h gives \( 240 \div 3 = 80 \) km/h. Make sure the units match — if distance is in km and time in minutes, convert minutes to hours first (divide by 60) before dividing, or you will get a wrong answer.

Why can't I just average the speeds of each part of the trip?

Averaging the speeds of each leg usually gives the wrong result, because you spend different amounts of time at each speed. The correct method is total distance divided by total time. For instance, driving 60 km at 60 km/h and 60 km back at 20 km/h averages 30 km/h, not 40 km/h — you spent far longer on the slow leg. Only when all legs take exactly the same time does a simple average work.

What is a typical average speed for walking, cycling or driving?

As rough real-world figures: walking is about 5 km/h (3 mph), commuter cycling 15–20 km/h (9–12 mph), and city driving often 25–40 km/h (15–25 mph) due to traffic and lights. Highway driving typically averages 90–110 km/h (55–70 mph). Note that these are door-to-door averages including stops — the moving-time average is higher.

How do I convert between km/h, mph and m/s?

Use these factors: \( 1\ \text{km/h} = 0.27778\ \text{m/s} \), \( 1\ \text{mph} = 1.609344\ \text{km/h} \), and \( 1\ \text{m/s} = 3.6\ \text{km/h} \). So 100 km/h ≈ 62.1 mph ≈ 27.8 m/s, and 60 mph ≈ 96.6 km/h. This calculator converts everything to metres and seconds internally and shows the result in all three units, so you can also use it as a quick speed converter.

Should stops and breaks be included in the time?

Yes, if you want the true door-to-door average speed — a 20-minute lunch break during a 2-hour trip is part of the elapsed time. If you only care about how fast you moved while driving, subtract all stops from the total time before entering it. Just be consistent: mixing moving-time with total distance makes the result meaningless for planning.

Why can average velocity be zero or negative while average speed is not?

Average speed uses the full path length, so it is always positive. Average velocity uses net displacement, so if you return to your starting point it is exactly zero, and if you end up behind the start it is negative. Walking 3 km east then 3 km west in one hour gives 6 km/h average speed but 0 km/h average velocity — you moved, but changed position by nothing.

What happens if I enter zero distance or zero time?

Zero distance is valid: the average speed is simply 0, since no ground was covered (e.g. you stood still for an hour). Zero time is not valid — dividing by zero is undefined, and the calculator will ask for a time greater than zero. If a segment took only moments, enter a small positive value such as 0.01 s rather than leaving it out, so the segment count still matches.