Science & Engineering
Speed Distance Time
Calculate speed, distance, or time from any two known values.
The speed-distance-time triangle is one of the most universally useful formulas in physics. Whether you're planning a road trip, analyzing sports performance, or solving physics problems, this calculator handles all three variations.
Speed
50.00 km/h
- formula
- Speed = 100 / 2
Formula and method
Speed = Distance / Time ; Distance = Speed × Time ; Time = Distance / Speed
The three forms of the SDT triangle. Speed is measured in distance units per time unit. All three can be derived from any two known values.
Worked examples
Road trip: Toronto to Montreal
- Solve For:
- Time
- Value 1:
- 541
- Value 2:
- 100
- Unit:
- km/h
Time: 5.410 hours
Running speed from race time
- Solve For:
- Speed
- Value 1:
- 10
- Value 2:
- 0.833
- Unit:
- km/h
Speed: 12.00 km/h
Assumptions and limits
- Constant speed (uniform motion)
- Consistent units throughout
This tool provides an educational estimate. Rules, rates and personal circumstances can change the answer. Review the assumptions before relying on a result. Report a correction.
Common mistakes to avoid
- Mixing units — if distance is in km but time is in minutes, you must convert to hours first.
- Using average speed for non-uniform motion — average speed = total distance / total time, not the average of two speeds.
- Confusing speed and velocity — speed is scalar (magnitude only); velocity is a vector (has direction).
Frequently asked questions
How long does it take to drive 500 km at 100 km/h?
500 km / 100 km/h = 5 hours. But add 10-15% for stops, traffic, and fuel — so plan for 5.5-6 hours.
What is the speed of light in km/h?
Approximately 1,079,252,848 km/h (about 1.08 billion km/h or 670 million mph). In m/s, it is exactly 299,792,458 m/s.
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