Speed Calculator

Calculate speed, distance, or time using the formula v = d/t. Enter any two values to find the third. Perfect for travel planning, physics problems, and racing calculations.

Speed

50.00 mph

Distance

150.00 mi

Time

3.0000 hours

Speed, Distance, and Time Relationship

The relationship between speed, distance, and time is one of the most fundamental formulas in physics: distance = speed × time. This formula works for any type of motion with constant speed. For varying speeds, the formula gives average speed over the entire journey.

Typical Speeds Reference

Activitymphkm/hm/s
Walking pace3-45-6.51.3-1.8
Running (jog)5-68-102.2-2.7
Running (sprint)10-1516-244.5-6.7
Cycling12-1820-305.5-8.3
Car (city)25-3540-5611-16
Car (highway)55-7589-12125-34
Commercial jet550885246
Speed of sound7671,235343

Real World Speed Examples

Walking speed for an average adult is about 3-4 mph (5-6.5 km/h), while a brisk jog reaches 6-10 mph (10-16 km/h). On the highway, typical speeds range from 55-70 mph (89-113 km/h), though limits vary by country. The speed of sound at sea level is approximately 767 mph (1,235 km/h), which is why supersonic aircraft create sonic booms when they exceed this threshold.

These reference speeds help put your calculations into perspective. When planning a road trip, knowing that highway speeds around 65 mph cover about 65 miles per hour of driving helps estimate arrival times. For runners, maintaining a 6 mph pace means completing a mile in 10 minutes. Understanding these benchmarks makes speed calculations more intuitive in everyday life.

Frequently Asked Questions

How do I calculate average speed?
Average speed is calculated by dividing total distance by total time: v = d / t. For example, driving 150 miles in 3 hours gives an average speed of 50 mph. This differs from instantaneous speed, which is the speed at a specific moment. Average speed accounts for all stops and slowdowns during the trip.
What is the difference between speed and velocity?
Speed is a scalar quantity that only measures how fast an object is moving, while velocity is a vector that includes both speed and direction. Speed is always positive, but velocity can be negative if moving in the opposite direction. For example, a car driving at 60 mph north has a speed of 60 mph and a velocity of 60 mph north.
How do I convert between mph and km/h?
To convert miles per hour to kilometers per hour, multiply by 1.60934. To convert km/h to mph, divide by 1.60934. For quick mental math: 60 mph ≈ 100 km/h, 30 mph ≈ 50 km/h, and 100 mph ≈ 160 km/h. For more precise conversions, use our Mile to KM Converter tool.
What is instantaneous speed vs average speed?
Instantaneous speed is the speed at a specific moment, like what your car's speedometer shows. Average speed is total distance divided by total time. If you drive at 60 mph for one hour and stop for 30 minutes, your instantaneous speed varies, but your average speed for the whole trip is 40 mph (60 miles in 1.5 hours).
How do I calculate speed for multi-leg journeys?
For journeys with multiple segments at different speeds, calculate each segment's time separately (distance ÷ speed), add all times together, then divide total distance by total time. For example, 30 miles at 30 mph (1 hour) plus 60 miles at 60 mph (1 hour) equals 90 miles in 2 hours, or 45 mph average.

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