Free Speed, Distance & Time Calculator
Calculate speed, distance, or travel time instantly. Supports mph, km/h, knots, and m/s with automatic unit conversion.
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Speed
66.67 mph / 107.29 km/h
Formula
Speed = Distance ÷ Time | Distance = Speed × Time | Time = Distance ÷ SpeedHow to Calculate Speed, Distance, or Travel Time
The relationship between speed, distance, and time is one of the most practical formulas in everyday life. Whether you're planning a road trip, estimating delivery times, or solving physics problems, the core equation is simple: Speed = Distance ÷ Time. This calculator lets you solve for any of the three variables.
Select what you want to calculate, enter the two known values with their units, and get an instant result. The calculator supports miles, kilometers, meters, feet, and multiple speed units including mph, km/h, m/s, and knots.
Understanding Speed Units
- mph (miles per hour) — standard in the US and UK for road speeds
- km/h (kilometers per hour) — used in most countries worldwide for road speeds
- m/s (meters per second) — the SI unit used in science and engineering
- knots — nautical miles per hour, used in aviation and maritime navigation
Practical Speed References
Here are common speeds to help you estimate and verify your calculations:
- Walking: 3-4 mph (5-6 km/h)
- Cycling: 10-15 mph (16-24 km/h)
- City driving: 25-35 mph (40-56 km/h)
- Highway driving: 55-75 mph (88-120 km/h)
- Commercial airplane: 460-575 mph (740-925 km/h)
- Speed of sound: 767 mph (1,235 km/h)
Tips for Accurate Travel Time Estimates
When planning trips, remember that your average speed is always lower than your cruising speed. Traffic lights, stops, congestion, and speed zone changes reduce your overall average. For highway-only trips, use about 90% of the speed limit as your average. For mixed city and highway driving, estimate 60-70% of the highway speed limit.
For long road trips, add 15-20 minutes per 2 hours for fuel stops, rest breaks, and food. A GPS-estimated arrival time is usually more accurate than a simple distance-divided-by-speed calculation because it accounts for real-time traffic conditions.
Frequently Asked Questions
How do I calculate travel time for a road trip?
Switch to Time mode, enter your total distance and average speed. For example, a 450-mile trip at 65 mph takes about 6 hours 55 minutes. Add 10-15% for stops, traffic, and speed changes — so plan for about 8 hours total.
How do I convert mph to km/h?
Multiply mph by 1.60934 to get km/h, or divide km/h by 1.60934 to get mph. Quick mental math: multiply mph by 1.6. So 60 mph ≈ 96 km/h. This calculator shows both units automatically.
What is the average walking speed?
The average adult walks at about 3.1 mph (5 km/h). Brisk walking is 3.5-4.5 mph. Running speed varies widely: casual jogging is 4-6 mph, competitive marathon pace is about 6-8 mph, and elite sprinters reach 23-28 mph.
How fast does sound travel?
Sound travels at about 767 mph (1,235 km/h) at sea level in dry air at 68°F. This is known as Mach 1. Sound travels faster through water (~3,350 mph) and even faster through steel (~11,500 mph).
What speed units do ships and aircraft use?
Ships and aircraft use knots (nautical miles per hour). One knot equals 1.15 mph or 1.852 km/h. A nautical mile is based on one minute of latitude, which is why it's preferred for navigation. This calculator supports knots.