Speed Calculator
Solve for speed, distance, or time — enter any two values and calculate the third
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Quick summary
The speed calculator uses the fundamental relationship: Distance = Speed × Time. Given any two values, it solves for the third. All units are converted to SI base units (meters, seconds) for calculation, then converted back to the desired output unit.
Reviewed by Simple Calculators TeamLast reviewed
How to use this calculator
- Enter the inputs requested by the calculator.
- Choose the units or options that match your situation and review the assumptions.
- Run or update the calculation to see the result.
- Review the result, breakdown, and formulas shown on the page.
- Check the inputs, units, dates, and limitations before saving or sharing the result.
Speed Formulas & Conversions
Speed, Distance, Time Triangle
- D
- Distance
- S
- Speed
- T
- Time
Worked example
Car traveling 100 km in 1.5 hours
- Given
- D = 100 kmT = 1.5 h
- Calculation
- Result
- ≈ 66.67 km/h
Speed Unit Conversions
- mph
- Miles per hour
- km/h
- Kilometers per hour
- m/s
- Meters per second
Worked example
Convert 60 mph
- Given
- mph = 60
- Calculation
- Result
- ≈ 96.56 km/h
Frequently asked questions
How do I calculate average speed?
Average speed = Total Distance / Total Time. If you drive 120 km in 2 hours, your average speed = 120 / 2 = 60 km/h. Note that average speed is not the same as average velocity (which accounts for direction).
What is the difference between speed and velocity?
Speed is a scalar (magnitude only): how fast you're going. Velocity is a vector: speed plus direction. 60 mph north and 60 mph south have the same speed but different velocities.
How fast is 100 km/h in mph?
100 km/h ÷ 1.60934 ≈ 62.14 mph. A quick approximation: km/h × 0.621 ≈ mph.
What is a knot?
A knot is one nautical mile per hour. 1 knot = 1.852 km/h = 1.151 mph. Knots are used in maritime and aviation navigation.
Key terms
- Speed
- The rate of change of distance over time. Speed = Distance / Time.
- Velocity
- Speed with a specified direction (a vector quantity).
- Knot
- A unit of speed equal to 1 nautical mile per hour (≈ 1.852 km/h).
- Mach Number
- Speed relative to the speed of sound (≈ 340 m/s at sea level). Mach 1 ≈ 1,235 km/h.
Methodology, sources & limitations
This page shows the formula, assumptions, and limitations used for this estimate. Rates, thresholds, and other time-sensitive inputs can change, so verify them against the relevant official source before relying on a result.
For our review approach and the primary sources we consult, see the methodology and source policy. If you spot an outdated figure or formula, please contact us with a correction.