To calculate speed, divide the distance traveled by the time taken:
Speed = Distance ÷ Time
For example, if a car travels 180 miles in 3 hours:
Speed = 180 ÷ 3
Speed = 60 miles per hour
This gives the average speed over the full trip.
What Is the Formula for Speed?
The standard speed equation is:
Speed = Distance ÷ Time
In symbols:
s = d ÷ t
Where:
- s = speed
- d = distance traveled
- t = elapsed time
The result is expressed as distance per unit of time.
Examples include:
- miles per hour (mph);
- kilometers per hour (km/h);
- meters per second (m/s);
- feet per second (ft/s).
This formula is one part of the broader Distance, Speed and Time Formula relationship.
How Do You Calculate Speed Step by Step?
Use four steps.
Step 1: Identify the Distance
Find the total distance traveled.
Example:
Distance = 150 miles
Step 2: Identify the Time
Find the total elapsed time.
Example:
Time = 2.5 hours
Step 3: Make Sure the Units Match
If distance is in miles and you want miles per hour, the time must be expressed in hours.
Here:
2.5 hours
is already suitable.
Step 4: Divide Distance by Time
Use:
Speed = Distance ÷ Time
So:
Speed = 150 ÷ 2.5
Speed = 60 mph
The average speed is 60 miles per hour.
Why Is Speed Equal to Distance Divided by Time?
Speed describes how much distance is covered during a given amount of time.
Suppose an object travels:
120 miles
in:
2 hours
That means it covers, on average:
120 ÷ 2 = 60 miles
during each hour.
Therefore:
Speed = 60 miles per hour
The same relationship applies to any compatible units.
For example:
100 meters ÷ 20 seconds = 5 meters per second
What Is Average Speed?
Average speed is:
Average Speed = Total Distance ÷ Total Elapsed Time
OpenStax defines average speed as total distance traveled divided by the time during which the motion occurs.
For example:
Total Distance = 300 miles
Total Time = 5 hours
Then:
Average Speed = 300 ÷ 5
Average Speed = 60 mph
The object does not need to travel at 60 mph every second.
It may travel:
- faster during some parts;
- slower during others;
- stop temporarily.
The final 60 mph value describes the entire trip.
Is the Speed Formula the Same as the Average Speed Formula?
For a completed trip, yes:
Average Speed = Total Distance ÷ Total Time
When people ask how to calculate speed from the total trip distance and total trip time, they are normally calculating average speed.
Instantaneous speed is different.
Instantaneous speed describes how fast something is moving at a specific moment.
For example, a car speedometer shows approximately instantaneous speed rather than average trip speed.
Example: Calculate Speed in Miles Per Hour
Suppose:
Distance = 240 miles
Time = 4 hours
Use:
Speed = Distance ÷ Time
Speed = 240 ÷ 4
Speed = 60 mph
The average speed is:
60 miles per hour
Example: Calculate Speed in Kilometers Per Hour
Suppose a vehicle travels:
350 km
in:
5 hours
Then:
Speed = 350 ÷ 5
Speed = 70 km/h
The average speed is 70 kilometers per hour.
Example: Calculate Speed in Meters Per Second
Suppose a runner covers:
400 meters
in:
50 seconds
Use:
Speed = 400 ÷ 50
Speed = 8 m/s
The runner's average speed is:
8 meters per second
How Do You Calculate Speed When Time Is in Minutes?
Convert the minutes into the time unit required by the speed.
If you want miles per hour, convert minutes to hours.
Use:
Hours = Minutes ÷ 60
For example:
Distance = 30 miles
Time = 45 minutes
Convert the time:
45 ÷ 60 = 0.75 hours
Then:
Speed = 30 ÷ 0.75
Speed = 40 mph
How Do You Calculate Speed for 30 Minutes?
Suppose:
Distance = 25 miles
Time = 30 minutes
Convert:
30 minutes = 0.5 hours
Then:
Speed = 25 ÷ 0.5
Speed = 50 mph
A common mistake is to divide:
25 ÷ 30
without converting minutes to hours first.
That would not produce miles per hour.
How Do You Calculate Speed When Time Is in Seconds?
If the distance is in meters and time is in seconds, no conversion is needed to get meters per second.
For example:
Distance = 200 meters
Time = 25 seconds
Then:
Speed = 200 ÷ 25
Speed = 8 m/s
If you want the result in km/h, convert afterward:
km/h = m/s × 3.6
So:
8 × 3.6 = 28.8 km/h
How Do You Convert Minutes and Seconds Into Hours?
Suppose the travel time is:
2 hours 30 minutes
Convert the minutes:
30 ÷ 60 = 0.5 hours
Then:
Total Time = 2 + 0.5
Total Time = 2.5 hours
For:
150 miles in 2 hours 30 minutes
calculate:
Speed = 150 ÷ 2.5
Speed = 60 mph
How Do You Calculate Speed From Hours, Minutes and Seconds?
Convert the full time into one unit.
Suppose:
Distance = 10 miles
Time = 1 hour 15 minutes 30 seconds
Convert minutes:
15 ÷ 60 = 0.25 hours
Convert seconds:
30 ÷ 3,600 ≈ 0.00833 hours
Then:
Total Time ≈ 1 + 0.25 + 0.00833
Total Time ≈ 1.25833 hours
Now:
Speed = 10 ÷ 1.25833
Speed ≈ 7.95 mph
CalculatorSoup similarly supports hours, minutes, seconds, and combined time formats when solving speed-distance-time problems.
Why Must Distance and Time Units Be Compatible?
Units determine the meaning of the result.
If:
Distance = miles
and:
Time = hours
then:
Speed = miles per hour
If:
Distance = kilometers
and:
Time = hours
then:
Speed = kilometers per hour
If:
Distance = meters
and:
Time = seconds
then:
Speed = meters per second
Problems occur when you mix units without converting them first.
For example:
100 miles ÷ 120 minutes
does not immediately give mph.
Convert:
120 minutes = 2 hours
Then:
Speed = 100 ÷ 2
Speed = 50 mph
How Do You Calculate MPH?
Miles per hour means:
Miles traveled ÷ Hours elapsed
So:
MPH = Miles ÷ Hours
For example:
275 miles ÷ 5 hours = 55 mph
The average speed is:
55 mph
How Do You Calculate KM/H?
Use:
km/h = Kilometers ÷ Hours
For example:
Distance = 420 km
Time = 6 hours
Then:
Speed = 420 ÷ 6
Speed = 70 km/h
How Do You Calculate Meters Per Second?
Use:
m/s = Meters ÷ Seconds
For example:
Distance = 100 meters
Time = 12.5 seconds
Then:
Speed = 100 ÷ 12.5
Speed = 8 m/s
How Do You Convert MPH to KM/H?
Use:
km/h = mph × 1.609344
For example:
60 mph × 1.609344
≈ 96.56 km/h
Calculator.net gives the same standard relationship, with 1 mph approximately equal to 1.60935 km/h.
How Do You Convert KM/H to MPH?
Use:
mph = km/h × 0.621371
For example:
100 km/h × 0.621371
≈ 62.14 mph
How Do You Convert M/S to KM/H?
Use:
km/h = m/s × 3.6
For example:
15 m/s × 3.6
= 54 km/h
How Do You Convert M/S to MPH?
Use approximately:
mph = m/s × 2.23694
For example:
10 m/s × 2.23694
≈ 22.37 mph
Speed Conversion Quick Reference
| From | To | Formula |
|---|---|---|
| mph | km/h | mph × 1.609344 |
| km/h | mph | km/h × 0.621371 |
| m/s | km/h | m/s × 3.6 |
| km/h | m/s | km/h ÷ 3.6 |
| m/s | mph | m/s × 2.23694 |
| mph | m/s | mph × 0.44704 |
What Is the Difference Between Speed and Velocity?
Speed and velocity are not identical in physics.
Speed describes how fast something moves.
Velocity describes how fast something moves and in which direction.
OpenStax describes speed as a scalar quantity and velocity as a vector quantity that includes direction.
For example:
60 mph
is a speed.
60 mph north
contains both magnitude and direction and therefore describes velocity more completely.
Can You Calculate Velocity With Distance and Time?
Not correctly from distance alone.
Average velocity uses displacement, not total distance:
Average Velocity = Displacement ÷ Time
Suppose you walk:
2 miles east
and then:
2 miles west
Total distance:
4 miles
Final displacement:
0 miles
So:
Average Speed = 4 ÷ Total Time
while:
Average Velocity = 0 ÷ Total Time = 0
This is why the workbook variation calculate velocity belongs on this page only as a distinction, not as a synonym for calculating speed.
Distance vs Displacement
Distance measures total path length.
Displacement measures the change from starting position to ending position.
Example:
Start at:
Point A
walk 5 miles east, then return 5 miles west.
Total distance:
10 miles
Displacement:
0 miles
Average speed can still be positive.
Average velocity over the entire journey is zero because the final position equals the initial position.
What Is Instantaneous Speed?
Instantaneous speed describes how fast an object is moving at one particular moment.
Examples include:
- speed shown on a car speedometer;
- speed of a runner at a particular second;
- speed of a moving object at a specific instant.
Average speed instead considers the entire selected interval.
OpenStax distinguishes average speed from instantaneous speed in exactly this way.
Can Average Speed Be Different From the Speedometer Reading?
Yes.
Suppose a road trip includes:
- 70 mph highway driving;
- 30 mph city driving;
- traffic stops.
Your speedometer may show 70 mph at one moment.
But the average speed for the full trip could be:
48 mph
because the total distance is divided by the total elapsed time.
Instantaneous speed and trip-average speed answer different questions.
How Do You Calculate Average Speed for a Road Trip?
Use:
Average Speed = Total Driving Distance ÷ Total Elapsed Time
Suppose:
Driving Distance = 300 miles
Elapsed Time = 5.5 hours
Then:
Average Speed = 300 ÷ 5.5
Average Speed ≈ 54.55 mph
For the road mileage itself, use the Driving Distance Calculator.
Should Stops Be Included in Average Speed?
It depends on what you mean by total time.
If you want the average speed for the entire trip, include all elapsed time, including stops.
Suppose:
Distance = 200 miles
Driving Time = 3 hours
Rest Stop = 30 minutes
Total elapsed time:
3.5 hours
Then:
Trip Average Speed = 200 ÷ 3.5
≈ 57.14 mph
If you exclude the stop:
Moving Average Speed = 200 ÷ 3
≈ 66.67 mph
Both values can be useful, but they describe different intervals.
How Do You Calculate Speed for Multiple Trip Segments?
Do not simply average the segment speeds unless the weighting makes that valid.
Instead use:
Average Speed = Total Distance ÷ Total Time
Suppose:
Segment 1
60 miles at 30 mph
Time:
60 ÷ 30 = 2 hours
Segment 2
60 miles at 60 mph
Time:
60 ÷ 60 = 1 hour
Total distance:
120 miles
Total time:
3 hours
Then:
Average Speed = 120 ÷ 3
Average Speed = 40 mph
The simple arithmetic average:
(30 + 60) ÷ 2 = 45 mph
is wrong for this trip.
The dedicated Average Speed Calculator Explained page covers multi-segment cases in more detail.
Why Is the Average Speed 40 MPH Instead of 45 MPH?
Because you spend more time traveling at the slower speed.
At 30 mph, the first 60 miles takes:
2 hours
At 60 mph, the second 60 miles takes:
1 hour
The slower section therefore contributes twice as much time to the trip.
Average speed must account for that unequal time.
How Do You Calculate Speed for Equal Time Intervals?
If equal amounts of time are spent at each speed, the ordinary arithmetic average works.
Suppose:
1 hour at 40 mph
and:
1 hour at 60 mph
Distance traveled:
40 + 60 = 100 miles
Total time:
2 hours
Average speed:
100 ÷ 2 = 50 mph
Arithmetic average:
(40 + 60) ÷ 2 = 50 mph
The values match because the time intervals are equal.
How Do You Calculate Speed for Equal Distances?
For equal distances traveled at two different speeds, the ordinary arithmetic mean is generally incorrect.
Suppose:
60 miles at 30 mph
and:
60 miles at 60 mph
we already found:
Average Speed = 40 mph
This equal-distance case is governed by the harmonic relationship between the speeds rather than the simple arithmetic mean.
For two equal-distance segments with speeds v₁ and v₂:
Average Speed = (2 × v₁ × v₂) ÷ (v₁ + v₂)
For:
v₁ = 30
v₂ = 60
Then:
Average Speed = (2 × 30 × 60) ÷ (30 + 60)
= 3,600 ÷ 90
= 40 mph
How Do You Calculate Required Speed to Arrive on Time?
Use:
Required Average Speed = Remaining Distance ÷ Remaining Time
Suppose:
Remaining Distance = 150 miles
Remaining Time = 2.5 hours
Then:
Required Average Speed = 150 ÷ 2.5
Required Average Speed = 60 mph
This is a mathematical average requirement, not a recommendation to exceed legal or safe speeds.
Actual driving should always follow applicable speed limits and road conditions.
How Fast Must You Travel 100 Miles in 2 Hours?
Use:
Speed = 100 ÷ 2
Speed = 50 mph
You need an average speed of 50 mph across the full two-hour interval.
How Fast Must You Travel 300 Miles in 5 Hours?
Use:
Speed = 300 ÷ 5
Speed = 60 mph
What Speed Is 5 Miles in 30 Minutes?
Convert:
30 minutes = 0.5 hours
Then:
Speed = 5 ÷ 0.5
Speed = 10 mph
What Speed Is 1 Mile in 10 Minutes?
Convert:
10 minutes = 10 ÷ 60 hours
= 1/6 hour
Then:
Speed = 1 ÷ (1/6)
Speed = 6 mph
What Speed Is 1 Mile in 20 Minutes?
Convert:
20 minutes = 1/3 hour
Then:
Speed = 1 ÷ (1/3)
Speed = 3 mph
This corresponds to a pace of 20 minutes per mile.
Speed vs Pace
Speed measures:
distance per unit time
Pace measures:
time per unit distance
For example:
Speed = 6 miles per hour
corresponds to:
Pace = 10 minutes per mile
The formulas are reciprocal when compatible units are used.
CalculatorSoup's current pace calculator likewise defines speed as distance divided by time and pace as time divided by distance.
How Do You Convert Speed to Pace?
For mph and minutes per mile:
Pace = 60 ÷ Speed
For example:
Speed = 6 mph
Then:
Pace = 60 ÷ 6
Pace = 10 minutes per mile
At:
3 mph
pace is:
60 ÷ 3 = 20 minutes per mile
How Do You Calculate Running Speed?
Use the same formula:
Running Speed = Distance ÷ Time
For example:
Distance = 5 km
Time = 25 minutes
Convert:
25 minutes = 25 ÷ 60 hours
≈ 0.41667 hours
Then:
Speed = 5 ÷ 0.41667
≈ 12 km/h
How Do You Calculate Walking Speed?
Use:
Walking Speed = Walking Distance ÷ Walking Time
For example:
Distance = 3 miles
Time = 1 hour
Then:
Walking Speed = 3 mph
For actual walking-path distance, use the Walking Route Distance Calculator rather than straight-line map distance.
How Do You Calculate Cycling Speed?
Suppose:
Distance = 30 miles
Time = 2 hours
Then:
Speed = 30 ÷ 2
Speed = 15 mph
Again, this is average speed over the full time interval.
How Does Speed Relate to Driving Distance?
To calculate average trip speed, you need the distance traveled.
For road travel, this should normally be driving distance, not straight-line geographic distance.
Suppose:
Straight-line distance = 100 miles
but:
Driving route = 125 miles
and:
Travel time = 2.5 hours
Using straight-line distance would give:
100 ÷ 2.5 = 40 mph
Using actual route distance gives:
125 ÷ 2.5 = 50 mph
For vehicle travel, the second calculation better represents average road speed.
Why Shouldn't You Use As-the-Crow-Flies Distance for Driving Speed?
Because a vehicle travels along the road route.
Average speed should use the distance actually traveled.
If you divide direct geographic separation by travel time, you are measuring a different ratio.
For route mileage, use the Driving Distance Calculator.
For direct geographic separation, use the Distance Calculator.
Does Traffic Change Average Speed?
Yes.
Traffic can increase elapsed time while the route distance remains similar.
Suppose:
Distance = 60 miles
Without congestion:
Time = 1 hour
Average speed:
60 mph
With congestion:
Time = 1.5 hours
Average speed:
60 ÷ 1.5
40 mph
The distance did not change, but average speed fell because the journey took longer.
Do Stops Reduce Average Speed?
Yes, when stop time is included in the elapsed time.
Suppose:
Distance = 100 miles
Driving time:
2 hours
Rest break:
30 minutes
Total time:
2.5 hours
Trip average:
100 ÷ 2.5 = 40 mph
Moving average excluding the stop:
100 ÷ 2 = 50 mph
Always define which time interval you are using.
Can Speed Be Zero?
Yes.
If an object is stationary during an interval:
Distance traveled = 0
so:
Speed = 0 ÷ Time
Speed = 0
What Happens if Time Is Zero?
The formula:
Speed = Distance ÷ Time
cannot be used with zero elapsed time for a nonzero distance because division by zero is undefined.
A finite distance cannot be traveled in zero time with a finite speed.
Can Speed Be Negative?
Ordinary speed is nonnegative because it describes magnitude.
Velocity can be positive or negative when direction is represented along an axis.
For example:
Velocity = −20 m/s
might indicate movement in the negative x-direction.
The corresponding speed is:
20 m/s
Can Time Be Negative?
Elapsed travel time is normally nonnegative.
A negative time difference may appear because of an incorrectly ordered timestamp calculation, but it should not represent ordinary trip duration.
Common Mistakes When Calculating Speed
Using the Wrong Formula
Use:
Speed = Distance ÷ Time
not:
Distance × Time
Forgetting to Convert Minutes
For mph, convert minutes to hours first.
Mixing Kilometers and Miles
Convert units before dividing.
Using Straight-Line Distance for a Road Trip
Use actual road mileage when calculating driving speed.
Ignoring Stops
Decide whether average speed should include the entire elapsed trip time.
Averaging Speeds Directly
Do not average segment speeds without considering time or distance weighting.
Confusing Speed With Velocity
Speed uses distance.
Average velocity uses displacement.
Rounding Too Early
Keep intermediate values precise and round the final result.
Speed Formula Quick Reference
Speed = Distance ÷ Time
Examples:
| Distance | Time | Average Speed |
|---|---|---|
| 120 miles | 2 hours | 60 mph |
| 150 miles | 3 hours | 50 mph |
| 300 km | 4 hours | 75 km/h |
| 100 m | 20 sec | 5 m/s |
| 30 miles | 45 min | 40 mph |
Which Formula Should You Use?
Use:
Speed = Distance ÷ Time
when distance and time are known.
Use:
Distance = Speed × Time
when speed and time are known.
Use:
Time = Distance ÷ Speed
when distance and speed are known.
See the Distance, Speed and Time Formula hub for all three relationships.
Frequently Asked Questions
How do you calculate speed?
Divide distance traveled by elapsed time:
Speed = Distance ÷ Time
What is the speed equation?
The standard speed equation is:
s = d ÷ t
where s is speed, d is distance, and t is time.
What is the formula for average speed?
Average Speed = Total Distance ÷ Total Time
How do I calculate speed in mph?
Divide miles traveled by time in hours.
How do I calculate speed when time is in minutes?
Convert minutes to hours first, then divide distance by time.
How do I calculate velocity?
Average velocity is displacement ÷ time, not distance ÷ time. Velocity also includes direction.
Is speed the same as velocity?
No. Speed is scalar and has magnitude only. Velocity is a vector and includes direction.
Is average speed the average of two speeds?
Not necessarily. Use total distance divided by total time unless the circumstances justify a simpler average.
What is the average speed for equal distances at 30 mph and 60 mph?
For equal distances, the average speed is 40 mph, not 45 mph.
Can speed be negative?
Ordinary speed cannot be negative. Signed motion is described using velocity.
What distance should I use for a road-trip speed calculation?
Use the actual driving-route distance rather than straight-line geographic distance.