Speed Calculator
Calculate speed, distance, or time using d = s x t.
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How It Works
Calculates speed from distance and time: Speed = Distance ÷ Time. Also calculates distance and time if the other two values are known. Use consistent units throughout.
Formula
s = d / tQuick Reference
Common calculations — results you can verify instantly.
300 miles in 5 hours
300/5
60 mph
Sound in air
Standard conditions
343 m/s = 767 mph
100km in 1.5hr
100/1.5
66.7 km/h
Tips & Shortcuts
Average speed = total distance ÷ total time (not average of speeds).
Sound travels at ~343 m/s in air. Light travels at ~300,000 km/s.
For unit conversions: 1 mph = 1.609 km/h. 1 m/s = 3.6 km/h.
Common Mistakes
Averaging speed by averaging two speed values
If you drive 60 mph for 1h and 120 mph for 1h, average speed = 270 miles ÷ 2h = 90 mph, not (60+120)/2 = 90 mph (coincidentally same, but not always).
Mixing units (miles and km, hours and minutes)
Convert everything to the same unit system before calculating.
Frequently Asked Questions
Time = 300 ÷ 60 = 5 hours.
Mach 1 = the speed of sound ≈ 343 m/s = 1,235 km/h = 767 mph at sea level, 20°C.
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