A speed, distance, time calculator solves the relation speed = distance ÷ time for whichever variable is missing. Pick what you want to find, enter the other two values in matching units, and the calculator returns the third.
Useful for trip planning (how long will the drive take?), running pace math, training calculations, physics homework, and any real-world setting where two of speed/distance/time are known and the third is needed. Inputs default to mph and miles for US-style use; the math is identical for kph and km.
Key takeaway
The three quantities form a triangle: D = S × T, S = D ÷ T, T = D ÷ S. Each is the same equation rearranged. Once you internalize the triangle, every speed-distance-time problem reduces to identifying which variable you don't know and applying the right rearrangement. The relationship is one of the simplest in physics and arguably the most useful in everyday life.
How it's calculated
The three forms of the equation:
- Speed = Distance ÷ Time, when you know how far and how long
- Distance = Speed × Time, when you know how fast and how long
- Time = Distance ÷ Speed, when you know how far and how fast
Units must be consistent: if speed is in mph and distance in miles, time comes out in hours. For minutes, multiply hours by 60. For metric (kph and km), the relationships are identical.
Mental anchors for trip planning:
- At 60 mph, 1 mile takes 1 minute. Easy ratio.
- At 30 mph, 1 mile takes 2 minutes.
- At 70 mph, 1 mile takes ~51 seconds (close to 1 minute, slightly under).
- Running pace: 6 mph = 10-min mile; 7.5 mph = 8-min mile; 10 mph = 6-min mile.
These anchor points let you estimate trips without arithmetic, once you know the per-mile time, total trip time is just per-mile × miles.
Source: Standard kinematic identity, speed = distance ÷ time
Examples
Find time: 120 miles at 60 mph
- Solve for Time
- Speed (mph) 60 mph
- Distance (mi) 120 mi
- Time (hours) 0 hr
A 120 mile trip at a steady 60 mph takes 2 hours, no surprise. Anchor: 60 mph = 1 mile per minute, so 120 miles = 120 minutes = 2 hours. Real trips are slower because of stops, traffic, and varying speeds, pad by 10-20% for realistic planning.
Find speed: 5 km in 25 minutes
- Solve for Speed
- Speed (mph) 0 mph
- Distance (mi) 5 mi
- Time (hours) 0.4167 hr
A 5 km run completed in 25 minutes (= 0.4167 hours) gives an average speed of 12 kph, a respectable amateur 5K pace. Equivalently, 5 minutes per kilometer or about a 4.83-minute kilometer. Marathon pace for a sub-3:30 finish is roughly 9.6 mph / 15.4 kph, for reference.
Frequently asked questions
How do I calculate speed, distance, or time?
Pick which one you don't know and use the matching formula:
- Speed = Distance ÷ Time
- Distance = Speed × Time
- Time = Distance ÷ Speed
Keep units consistent (mph + miles → hours, or kph + km → hours). For minutes, multiply hours by 60. For seconds, multiply by 3,600. The arithmetic is the same; only the pre-conversion of units changes the final number.
How do I convert pace (min/mile) to speed (mph)?
Speed (mph) = 60 ÷ pace (min/mile). So an 8-minute mile is 60 ÷ 8 = 7.5 mph; a 10-minute mile is 6 mph; a 6-minute mile is 10 mph. Reverse: pace = 60 ÷ speed. The 60-and-divide relationship comes from "60 minutes per hour", pace is just the inverse of speed when expressed per unit distance.
How do I plan a road trip with stops?
Use this calculator for the driving-only time, then add stop time. Rule of thumb: add 15-20% for typical highway driving with bathroom and meal stops. Long trips with kids: add 25-30%. Trips with potential traffic (urban approach, holidays): add another 15-20% buffer. So a 600-mile drive at 65 mph takes ~9.2 hours of driving, plan for 11-12 hours total elapsed.
What's the difference between speed and velocity?
Speed is a scalar, just magnitude, like "60 mph." Velocity is a vector, magnitude plus direction, like "60 mph north." For most everyday calculations they're interchangeable. The distinction matters in physics (where direction affects the math) and in navigation (where heading is as important as speed). This calculator computes speed, the same number that velocity would give if you don't care about direction.