Speed Distance Time Calculator
Solve for speed, distance, or time using the fundamental relationship: Distance = Speed × Time.
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How to use this calculator
Set the unknown to 0 and the calculator solves for it using D = S × T.
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Enter two known values (distance, speed, or time).
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Set the unknown value to 0.
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The calculator solves for the missing quantity.
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Results are shown in both km and miles.
Frequently asked questions
How do I convert km/h to m/s?
Divide by 3.6. 90 km/h ÷ 3.6 = 25 m/s. Conversely, multiply m/s by 3.6 to get km/h. 30 m/s × 3.6 = 108 km/h. This conversion is essential in physics problems that use SI units.
What is average speed vs instantaneous speed?
Average speed = total distance / total time. Instantaneous speed is speed at a precise moment (shown on a speedometer). A car averaging 90 km/h over 3 hours covered 270 km total, but its speed varied throughout the journey.
How do I calculate travel time with stops?
Calculate driving time using D/S, then add stop time separately. Total trip time = driving time + stop time. The calculator computes driving time only — stops must be added manually.
What is the difference between speed and velocity?
Speed is scalar (magnitude only): 90 km/h. Velocity is vector (magnitude + direction): 90 km/h north. Average speed uses total distance; average velocity uses displacement (straight-line distance from start to end). They differ when direction changes.
Speed, distance, and time calculations
How to use the speed distance time
This speed distance time gives you instant, accurate results — no registration or download required. Enter your values above and get your result in seconds. The tool is free, works on all devices, and keeps your data private — nothing is stored or shared.
How the speed distance time works
The speed distance time uses standard formulas used in financial planning, budgeting, and investment decisions. Enter your inputs, and the tool calculates the result instantly in your browser. No server-side processing means your data stays on your device. Results update in real time as you change inputs.
The speed-distance-time triangle
Cover the unknown in the triangle to get its formula: cover D → D = S × T; cover S → S = D/T; cover T → T = D/S. This mnemonic is taught in schools worldwide and works for any consistent set of units (km + km/h + hours, or miles + mph + hours).
Relative speed
When two objects move in the same direction, relative speed = |S₁ − S₂|. When moving toward each other (opposite directions), relative speed = S₁ + S₂. If a train at 80 km/h overtakes another at 60 km/h, the relative speed is 20 km/h. These problems are common in competitive exams.
Speed in physics vs everyday use
Physics uses metres per second (m/s) in SI units. Daily life uses km/h (most countries) or mph (USA, UK). Sound travels ~343 m/s (1,234 km/h) at sea level. Light travels ~300,000 km/s. An airliner cruises at ~900 km/h — less than 0.001% the speed of light.
Speed distance time: how it works
Built on well-established mathematical principles, this tool delivers accurate results for students, researchers, and professionals. Enter your values and get instant clarity without specialist software or manual arithmetic.
Who uses this tool?
Teachers, students, engineers, and data analysts use it to verify calculations, check homework, and solve problems faster. It is intuitive enough for beginners while comprehensive enough for professional use.
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Results are estimates for informational purposes only and do not constitute professional financial, medical, legal, or technical advice. Read full disclaimer →