Enter any two values and solve for the third. Supports multiple speed units.
The SDT Triangle
| Find | Formula | Example |
|---|
| Speed | S = D ÷ T | 150 mi ÷ 2.5h = 60 mph |
| Distance | D = S × T | 60 mph × 3h = 180 miles |
| Time | T = D ÷ S | 240 mi ÷ 60 mph = 4h |
Speed Unit Conversions
| From → To | Multiply by |
|---|
| mph → km/h | 1.60934 |
| km/h → mph | 0.62137 |
| mph → m/s | 0.44704 |
| knots → mph | 1.15078 |
| knots → km/h | 1.852 |
Real-World Speed References
Walking: 3-4 mph. Cycling: 12-15 mph. City driving: 25-35 mph. Highway: 55-75 mph. Commercial aircraft: 550-580 mph (cruising). Speed of sound at sea level: 767 mph. Light: 186,282 miles per second. These benchmarks make it easier to sanity-check your calculations.
How to Use This Speed Distance Time Calculator
Enter any two of speed, distance, or time. The calculator solves for the third value and provides unit conversions.
Formula & How It Works
Distance = Speed × Time. Speed = Distance / Time. Time = Distance / Speed. Unit conversions: 1 mile = 1.609 km, 1 km/h = 0.621 mph.
Calculation Example
Driving 250 miles at 65 mph: Time = 250/65 = 3.85 hours (3h 51min). A marathon (42.195 km) in 4 hours = 10.55 km/h pace.
Expert Tips
For multi-segment trips, calculate each segment separately and sum the times (you cannot average speeds directly for segments of different distances). Always account for stops and traffic in real-world planning.