This calculator finds one of the three values when you have the other two: speed, distance, or time. It is useful for travel planning, physics problems, and quick checks.
Core formulas
Find speed
speed = distance ÷ time
Example unit: km/h, m/s, mph.
Find distance
distance = speed × time
Find time
time = distance ÷ speed
Units and conversions
- Common speed units: kilometres per hour (km/h), metres per second (m/s), miles per hour (mph).
- 1 m/s = 3.6 km/h.
- 1 km/h ≈ 0.27778 m/s.
- 1 mph ≈ 1.60934 km/h.
- Make sure distance and time use matching units before calculating.
How to use
- Decide which value you need: speed, distance, or time.
- Enter the other two values in matching units.
- Apply the correct formula above or use the tool to compute.
- Convert units after if needed.
Worked examples
Example A — Find speed
Distance = 150 km. Time = 2 hours.
Speed = 150 ÷ 2 = 75 km/h.
Example B — Find distance
Speed = 60 km/h. Time = 1.5 hours.
Distance = 60 × 1.5 = 90 km.
Example C — Find time
Distance = 300 km. Speed = 100 km/h.
Time = 300 ÷ 100 = 3 hours.
Example D — Unit conversion (m/s to km/h)
Speed = 10 m/s. In km/h: 10 × 3.6 = 36 km/h.
Common mistakes
- Mixing units. Convert before using formulas.
- Dividing by zero. Time and speed must not be zero when used as divisors.
- Confusing hours and minutes. Convert minutes to hours by dividing by 60.
- Rounding too early. Keep precision until the final result.
Quick reference table
- speed = distance ÷ time
- distance = speed × time
- time = distance ÷ speed
FAQ
What if time is given in minutes?
Convert minutes to hours: minutes ÷ 60. Or convert hours to minutes by × 60 depending on units you want.
Can I use seconds?
Yes. Use seconds for time and metres for distance. Then speed is in m/s.
What if speed is zero?
If speed is zero and distance is not zero, time is infinite. That situation is not physically meaningful for travel.
How do I convert km/h to mph?
Multiply km/h by 0.621371 to get mph.
What rounding is safe?
Two decimal places is fine for most uses. Keep more for precise work.
Can I handle variable speed?
Not directly. For variable speed use average speed = total distance ÷ total time.
How to compute average speed over stops?
Use total distance divided by total time, including stops, to get average speed.
Does uphill or wind affect calculation?
Yes. These factors change actual speed. The formula still holds for the measured speed value.
Is distance always a straight line?
No. Distance means the path length actually travelled. Use straight-line distance only when specified.
What if I mix metric and imperial?
Convert to one system before calculating. Mixing units leads to wrong results.
How to find speed from GPS data?
Compute distance between points and divide by time interval. Be careful with sampling errors.
Can time be negative?
No. Time is nonnegative. Negative time does not apply to these calculations.
How to show results in hours and minutes?
Split decimal hours. Example: 2.75 hours = 2 hours and 0.75×60 = 45 minutes.
What if I need instant speed?
Instant speed needs calculus and very small time intervals. The basic formulas give average speed.
Why is checking units important?
Units keep your math correct. Always match units for distance and time before using formulas.