Speed Distance Time Calculator
Solve speed, distance, or time problems easily. Just enter any two values to calculate the third. Perfect for trip planning, physics problems, or understanding motion.
What is the formula for speed, distance, and time?
The three fundamental formulas are: Speed = Distance / Time, Distance = Speed × Time, Time = Distance / Speed. These relationships form the "speed triangle" - a simple way to remember: cover what you want to find, and the remaining two show the formula. Example: To find speed, cover "Speed" and you see Distance/Time. These formulas work with any units as long as they're consistent (e.g., km and hours give km/h).
How do you calculate average speed?
Average speed = Total distance / Total time. Important: Don't average the speeds! Example: Drive 60 km at 30 km/h (2 hours), then 60 km at 60 km/h (1 hour). Wrong: (30+60)/2 = 45 km/h. Correct: 120 km / 3 hours = 40 km/h. Average speed is always weighted by time spent at each speed. For constant speed (no acceleration), average speed equals instantaneous speed. For varying speeds, you must use total distance and total time.
How do you convert between mph and km/h?
To convert: mph to km/h: multiply by 1.609 (60 mph ≈ 97 km/h). km/h to mph: divide by 1.609 or multiply by 0.621 (100 km/h ≈ 62 mph). Quick estimates: 50 mph ≈ 80 km/h, 60 mph ≈ 96 km/h, 70 mph ≈ 113 km/h. Remember: km/h values are always larger than mph values for the same speed because kilometers are shorter than miles. Speed limits vary by country: US uses mph, most others use km/h.
What is the difference between speed and velocity?
Speed is how fast you're moving (scalar - magnitude only): "60 mph". Velocity is speed with direction (vector - magnitude and direction): "60 mph north". In everyday language, they're used interchangeably. In physics, they're different: A car going around a circular track at constant speed has changing velocity (direction changes). Average velocity can be zero (round trip returns to start), but average speed cannot. This calculator focuses on speed/distance/time relationships regardless of direction.