This calculator solves the basic distance = speed × time relationship for whichever value you’re missing, given the other two.
Speed Distance Time Calculator
Solve the distance = speed × time relationship for whichever value you need.
What the Speed Distance Time Calculator Covers
This calculator covers all three variations of the classic speed-distance-time relationship — solving for time when you know distance and speed, solving for distance when you know speed and time, or solving for speed when you know distance and time.
This is a foundational calculation used across travel planning, physics problems, athletic pacing, and any situation involving constant-rate motion over a distance.
How Each Value Is Calculated
Formula
Time = Distance ÷ Speed
Distance = Speed × Time
Speed = Distance ÷ Time
Where all three variables use consistent units (for example, miles and hours together give mph; kilometers and hours together give km/h).
Worked Example (Solving for Time)
A distance of 120 miles at a speed of 60 mph.
Time = 120 ÷ 60 = 2 hours
Covering 120 miles at a constant 60 mph takes exactly 2 hours.
Worked Example (Solving for Distance)
A speed of 60 mph maintained for 2 hours.
Distance = 60 × 2 = 120 miles
This confirms the same relationship works in reverse: 2 hours at 60 mph covers 120 miles.
Why Unit Consistency Is Critical
This calculator doesn’t convert between unit systems automatically — entering miles for distance but minutes for time, for example, will produce an incorrect result. Always use consistent units throughout: miles with hours, or kilometers with hours, matched to whichever speed unit you want as the result.
Frequently Asked Questions
What units should I use for accurate results?
Match your distance and time units to the speed unit you want — miles and hours give mph, kilometers and hours give km/h, and meters and seconds give m/s; mixing unit systems within one calculation will give an incorrect result.
Does this assume constant speed throughout the trip?
Yes — this calculates an average speed, distance, or time based on a constant rate. If speed varies significantly during a trip, the result represents an average rather than the speed at any single moment.
How do I convert my answer to a different unit after calculating?
Use a standard unit conversion (for example, multiplying mph by 1.60934 to get km/h) on the result, since this calculator itself does not convert between different measurement systems.
Can I use this for calculating average pace in a race?
Yes — entering your race distance and finish time will solve for your average speed, which you can then convert to a more conventional pace format (like minutes per mile) if needed.
How do I solve for distance if I only know speed and arrival/departure times?
First subtract departure time from arrival time to get the elapsed time, then use that elapsed time along with your speed in the distance formula to find the total distance covered.
Is this the same formula used in basic physics classes?
Yes — this is the standard uniform-motion relationship taught in introductory physics, applicable whenever speed is constant over the distance or time being measured.