Speed, distance and time calculator: v = d / t
Solve v = d/t in all three directions. Enter two values among speed, distance and time, choose their units and calculate the third with SI conversion and a worked equation.
Enter exactly two values among speed, distance and time. Leave the quantity you want to calculate empty.
The calculation uses average speed over the distance travelled. It does not describe speed variations during the trip or vector velocity.
Results
Calculation details
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How does this tool work?
This calculator connects three fundamental motion quantities: average speed v, distance travelled d and elapsed time t. The relationship v = d/t lets you solve any one quantity from the other two. The tool works in all three directions, converts units automatically and shows the calculation. It is useful for physics exercises, travel problems, average vehicle speed, walking or cycling estimates, and any situation where total distance and elapsed time are meaningful.
Average speed is defined as total distance travelled divided by elapsed time: v = d/t. OpenStax states that the SI unit of speed is metre per second, m/s, although km/h, mph and other units are commonly used. If an object travels 150 km in 3 h, its average speed is 50 km/h.
The same relationship can be rearranged to find distance: d = vt. At 90 km/h for 2 h, the distance is 180 km. To find elapsed time, use t = d/v: travelling 12 km at 4 km/h takes 3 h.
Before solving the equation, Bethemesh converts the values to coherent SI units: metres, seconds and metres per second. The result is then converted back to the selected output unit. This prevents common errors when, for example, distance is in kilometres, time is in minutes and speed is requested in m/s.
Available units cover school and practical use: m/s, km/h, mph, knots and ft/s for speed; millimetres, centimetres, metres, kilometres, feet, yards, miles and nautical miles for distance; and milliseconds, seconds, minutes and hours for time.
Average speed is different from instantaneous speed. A 150 km trip completed in 3 h may average 50 km/h even if the vehicle sometimes moved faster, slower or stopped. This calculator does not reconstruct those changes; it uses total distance and total elapsed time only.
In physics, speed and velocity also differ. Speed based on distance is a scalar quantity. Average velocity is based on displacement divided by time and includes direction. A round trip can have a substantial travelled distance but zero net displacement. This calculator uses distance, not vector displacement.
How to use this tool
Choose the two known quantities
Fill two fields among speed, distance and elapsed time. Leave only the unknown quantity empty.
Select the correct units
Choose units that match the original data; each field may use a different measurement system.
Convert automatically to SI
The engine converts to m, s and m/s, then applies v = d/t, d = vt or t = d/v.
Review the calculation
The worked section shows the numerical substitution in SI units and the result in the unit you selected.
Speed, distance and time formulas
For average speed, travelled distance and elapsed time are linked by three equivalent equations.
Average speed
v = d ÷ t
Average speed is total distance travelled divided by elapsed time.
Distance
d = v × t
Distance is average speed multiplied by elapsed time.
Elapsed time
t = d ÷ v
Elapsed time is distance divided by average speed.
Common conversion
1 m/s = 3.6 km/h
This conversion connects the two speed units most often used in physics and everyday travel.
- v
- average speed, in m/s, km/h or another speed unit
- d
- total distance travelled
- t
- total elapsed time
These equations calculate average speed from distance and elapsed time. They do not describe instantaneous speed or vector velocity.
Use cases
Physics exercises
Check formulas, unit conversions and numerical answers in uniform-motion or average-speed problems.
Estimate travel time
Find a theoretical duration from a distance and an assumed average speed.
Calculate travelled distance
Determine how far an object travels over a known duration at a given average speed.
Compare speed units
Move between m/s, km/h, mph, knots and ft/s while keeping the same physical problem.
Examples
Calculate average speed
v = 150/3 = 50 km/h.
Input
d = 150 km; t = 3 hResult
v = 50 km/h ≈ 13.89 m/sCalculate distance
d = vt = 90 × 2 = 180 km.
Input
v = 90 km/h; t = 2 hResult
d = 180 kmCalculate elapsed time
t = d/v = 12/4 = 3 h.
Input
d = 12 km; v = 4 km/hResult
t = 3 hMinutes and kilometres
45 min = 0.75 h, so v = 10/0.75 ≈ 13.33 km/h.
Input
d = 10 km; t = 45 minResult
v ≈ 13.33 km/hMiles per hour
The engine can keep imperial units for display while solving through coherent SI units.
Input
d = 60 mi; t = 1.5 hResult
v = 40 mphTips and best practices
- One hour 30 minutes is 1.5 h, not 1.30 h. Convert minutes correctly before doing a manual calculation.
- To convert m/s to km/h, multiply by 3.6; to convert km/h to m/s, divide by 3.6.
- Average speed includes stops if the entered elapsed time covers the whole trip. Use moving time only if that is the average you want.
- Do not replace distance with displacement without checking the context; they can differ greatly for a round trip.
- If speed changes substantially during the journey, v = d/t still gives the overall average but says nothing about acceleration.
- Keep extra digits during conversion and round the final answer according to the precision of the original data.
Sources and references
- OpenStax, 2.2 Speed and Velocity (opens in a new tab), PhysicsPage in English
- BIPM — SI Brochure: units of time (opens in a new tab)Page in English
Frequently asked questions
What is the speed distance time formula?
The main relationship is v = d/t. Rearranging gives d = vt and t = d/v.
How do I calculate average speed?
Divide total distance travelled by total elapsed time: v = d/t. The units must be consistent.
How do I calculate distance from speed and time?
Multiply average speed by time: d = vt. For example, 80 km/h for 2.5 h gives 200 km.
How do I calculate time from distance and speed?
Divide distance by speed: t = d/v. A 100 km trip at 50 km/h takes 2 h.
What is the SI unit of speed?
The SI unit is metre per second, m/s. The BIPM lists speed and velocity as derived quantities expressed in m/s.
What is the difference between average and instantaneous speed?
Average speed describes an entire interval, while instantaneous speed describes how fast something is moving at a particular moment.
What is the difference between distance and displacement?
Distance is the total path length. Displacement is the directed change from initial to final position, so the two can differ.
Can I use minutes with kilometres?
Yes. The calculator converts them automatically; 45 minutes, for example, becomes 2700 seconds internally.
Are my values sent to a server?
No. Unit conversion and calculation run locally in your browser.
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