Speed, Distance & Time Calculator
Solve for speed, distance or time using the formula distance = speed × time. Enter any two values to find the third instantly.
How to use this tool
- Enter speed, distance and time in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your speed and the full breakdown beneath it.
The fundamental motion formula is d = s × t: distance equals speed times time. Rearranged: s = d/t and t = d/s. Enter any two to solve for the third.
Formula
distance = speed × time
Rearranged: speed = distance ÷ time | time = distance ÷ speed
Enter any two values (leave the unknown as 0) and the calculator solves for the third.
How it works
This calculator solves the fundamental kinematic relationship between speed, distance, and time. It detects which of the three values is zero (the unknown), then applies the appropriate rearrangement to find it. The formula assumes constant speed throughout the journey; it does not account for acceleration, deceleration, or varying velocity.
Worked example
- Given: distance = 100 m, time = 10 s. Speed is unknown (entered as 0).
- Apply the formula: speed = distance ÷ time = 100 ÷ 10.
- Calculate: speed = 10 m/s.
Speed = 10 m/s; Distance = 100 m; Time = 10 s
Common mistakes to avoid
- Mixing unit systems -- entering distance in kilometres and time in seconds gives a speed in km/s, not km/h.
- Leaving the unknown field at zero and forgetting the calculator interprets zero as the unknown, so entering a genuine zero value will cause an incorrect solve.
- Treating average speed as instantaneous speed -- the formula gives average speed over the total distance and time, not speed at any particular moment.
Key terms
- Speed
- The distance covered per unit of time, measured in m/s (or km/h, mph, etc.). Speed is a scalar quantity — it has magnitude but no direction.
- Distance
- The total length of the path travelled, measured in metres (m). It does not account for direction, unlike displacement.
- Time
- The duration of the journey, measured in seconds (s) in this calculator.
- Constant speed assumption
- This formula treats speed as uniform throughout. Real journeys involve acceleration and braking, so results represent average speed over the trip.
Frequently asked questions
- What units should I use?
- Any consistent units work — e.g. metres and seconds for SI, or km and hours for everyday driving. Just don't mix (e.g. km/h for speed with metres for distance).
- How do I convert km/h to m/s?
- Divide by 3.6. Example: 72 km/h ÷ 3.6 = 20 m/s.