Speed Calculator

The Formula

Speed is distance traveled per unit of time. The formula triangle shows the relationship between speed (S), distance (D), and time (T). Cover the variable you want to solve for.

Variable Definitions

How to Use This Calculator

1. 1

   Select what you want to solve for: Speed, Distance, or Time.

2. 2

   Enter the two known values with their units.

3. 3

   View the result in multiple unit formats including pace (min/mi or min/km).

Speed formula triangle: S = D / T

Understanding the Concept

The speed formula S = D/T is one of the most fundamental relationships in physics. Speed measures how fast an object covers distance over time. Pace — the inverse of speed — is commonly used in running and cycling, expressed as minutes per mile or minutes per kilometer. For example, running at 6 mph means a 10:00 min/mile pace. The speed of sound at sea level is about 767 mph (Mach 1), and typical highway speeds are 55-70 mph. Practical example: driving 180 miles in 3 hours means an average speed of 180 / 3 = 60 mph. The calculator also shows this as 96.6 km/h, 26.8 m/s, and 52.1 knots. Your pace would be 60 / 60 = 1.0 min/mile — but that is clearly wrong since pace is minutes per mile: pace = 60 / 60 = 1.0 minute per mile, or the more useful format: 60 minutes / 60 mph = 1 hour to travel 60 miles. For the running example: if you run 5 km in 25 minutes, your speed is 5 / (25/60) = 12 km/h, or about 7.5 mph, and your pace is 25 / 5 = 5 min/km (8:03 min/mile). Edge cases: when calculating speed over very short distances (like drag racing timing), convert everything to consistent units — a quarter mile (1,320 feet) in 10.5 seconds gives speed = 1,320 / 10.5 = 125.7 ft/s, which converts to 85.7 mph average, but the trap speed at the finish line (final speed) is typically much higher, around 130+ mph. For very slow speeds like tectonic plate movement (a few cm per year), the formula still works but the result is more meaningful in mm/year or inches/year. For circular motion, speed is still distance over time, but the distance is the circumference: speed = (2πr) / T where T is the period of rotation.

Frequently Asked Questions

Sources & References