Speed Calculator
Calculate speed, distance, or time when you know any two of the three variables.
Speed, distance, and time are related by the simplest formula in physics: distance = speed x time. The calculator solves for whichever variable you do not know. Most useful for travel planning, running/cycling pace conversion, and estimating arrival times when speed is variable.
Quick mental math: at 60 mph, you cover 1 mile per minute. At 65 mph, it is roughly 1 mile per 55 seconds. A 325-mile drive at 65 mph takes exactly 5 hours of driving time.
Unit conversions used
1 mile = 1.60934 km. 1 knot = 1.15078 mph. 1 m/s = 2.23694 mph. These conversions let you mix units freely in the calculator.
Practical uses
Road trips: distance and speed give estimated drive time (add 10-15% for stops, traffic, and slowdowns). Running: convert between pace (min/mile) and speed (mph) for treadmill and race planning. Cycling: average speed and route distance give ride time. Aviation: nautical miles and knots give flight time estimates. Boating: similar to aviation with knots and nautical miles.
Frequently asked questions
Why does actual drive time exceed the calculated time?
The formula assumes constant speed. Real drives involve traffic lights, speed limit changes, construction zones, slower speeds through towns, and mandatory stops. Add 15-20% to the calculated drive time for a more realistic road trip estimate. The Road Trip Total Cost calculator includes this buffer in its planning tools.