Speed Calculator

Whether you're analyzing a road trip, figuring out your running pace, or solving a physics problem, this speed calculator finds speed, distance, or time when you know the other two values.

What Does This Calculator Do?

Enter any two of the three variables — speed, distance, or time — and the calculator solves for the third. You can use miles, kilometers, meters, feet, hours, minutes, or seconds.

How to Use This Calculator

1. Select the variable you want to find (speed, distance, or time).
2. Enter the two known values with their units.
3. Click Calculate to get the result.

Speed Formula

Speed = Distance ÷ Time

Distance = Speed × Time

Time = Distance ÷ Speed

These three variations of the same formula cover any scenario — just rearrange for whatever you're solving for.

Example Calculations

What is the speed? You drove 150 miles in 2.5 hours.

• Speed = 150 ÷ 2.5 = 60 mph

How far did you travel? Driving at 65 mph for 3 hours.

• Distance = 65 × 3 = 195 miles

How long will it take? Cycling 30 km at 20 km/h.

• Time = 30 ÷ 20 = 1.5 hours (90 minutes)

Common Speed Unit Conversions

• 1 mph = 1.60934 km/h
• 1 km/h = 0.62137 mph
• 1 m/s = 3.6 km/h = 2.237 mph
• 1 knot = 1.852 km/h = 1.151 mph

Why Use This Calculator?

Speed problems come up in travel planning, sports analysis, physics homework, and logistics. Instead of rearranging formulas manually, this calculator does it for you with any unit combination.

Common Mistakes to Avoid

• Mixing units — if speed is in km/h, distance must be in km and time in hours. Always match your units.
• Confusing average speed with instantaneous speed — this calculator computes average speed over a total distance, not the speed at any specific moment.
• Forgetting stops and breaks — if calculating travel time for a long road trip, add time for fuel stops, meals, and rest.

Frequently Asked Questions

How do I calculate average speed for a round trip?

Average speed ≠ arithmetic mean of the two speeds. Use: Average speed = Total distance ÷ Total time. If you drove 60 mph there and 40 mph back (same distance), average speed = 48 mph, not 50.

What is the speed of light?

The speed of light in a vacuum is approximately 299,792,458 m/s (about 186,282 miles per second).

How do I convert mph to m/s?

Multiply by 0.44704. So 60 mph = 60 × 0.44704 = 26.82 m/s.

What is a good running speed?

Average recreational runners pace around 5–6 mph (8–10 min/mile). Elite marathon runners exceed 12–13 mph for 26.2 miles.

How do I calculate the distance if I know speed and time?

Multiply speed × time. At 70 mph for 90 minutes (1.5 hours): 70 × 1.5 = 105 miles.

Conclusion

Speed, distance, and time are interconnected — know any two and you can always find the third. This speed calculator handles the algebra so you can focus on planning, analyzing, or learning.

Related: Pace Calculator | Distance Calculator | Fuel Cost Calculator