Speed
Calculator
Calculate speed, distance, or time from any two values. Convert between mph, km/h, m/s, knots, and Mach. Includes running pace and real-world speed reference.
Speed of Everything
From snails to starlight — real-world speed comparisons.
Speed Limits & Records
Common speeds in mph, km/h, and m/s.
| Object / Context | mph | km/h | m/s | Notes |
|---|---|---|---|---|
| Average walking | 3.1 mph | 5.0 km/h | 1.39 m/s | Typical adult pace |
| Average running | 6–8 mph | 9.7–12.9 km/h | 2.7–3.6 m/s | Recreational runner |
| Usain Bolt (record) | 27.8 mph | 44.7 km/h | 12.4 m/s | Peak speed in 9.58s 100m |
| US highway limit | 65–75 mph | 105–121 km/h | 29.1–33.5 m/s | Varies by state |
| Fastest production car | ~300 mph | ~482 km/h | ~134 m/s | Bugatti Chiron Super Sport |
| Cheetah (top speed) | 70–75 mph | 112–120 km/h | 31–33 m/s | Fastest land animal |
| Commercial aircraft | ~575 mph | ~925 km/h | ~257 m/s | Cruise speed |
| Sound (sea level, 20°C) | 767 mph | 1,235 km/h | 343 m/s | Mach 1 |
| Concorde (retired) | 1,354 mph | 2,179 km/h | 605 m/s | Mach 2.04 |
| Speed of light (c) | 670,616,629 mph | 1,079,252,848 km/h | 299,792,458 m/s | Universal speed limit |
Nothing Can Travel Faster Than Light
Einstein's special relativity shows that as an object with mass accelerates toward the speed of light, the energy required approaches infinity. Light itself (photons) has no mass, which is why it travels at c. Even the fastest human-made objects — like the Parker Solar Probe at ~430,000 mph — are less than 0.1% of the speed of light.
Runners typically measure performance in pace (time per mile or per km) rather than speed. To convert speed to pace: Pace (min/mile) = 60 ÷ Speed (mph).
Example: 8 mph = 60 ÷ 8 = 7:30 min/mile. Common benchmarks: 5:00/mile = elite (12 mph), 8:00/mile = solid recreational (7.5 mph), 10:00/mile = beginner (6 mph). Marathon pace for a 4-hour finish ≈ 9:09/mile = 6.55 mph.
A knot equals one nautical mile per hour. 1 knot = 1.15078 mph = 1.852 km/h. It's the standard unit for ship and aircraft speeds. A nautical mile (1,852 m) equals one arcminute of latitude — a natural unit for navigation.
Average container ship: 14–25 knots. Naval destroyers: 30–35 knots. The fastest warship (SS United States) reached 38.32 knots (44.1 mph). Aircraft use knots for airspeed — a Boeing 737 cruises at ~450 knots (518 mph).
Speed, Distance & Time Formulas
Speed, distance, and time are three related quantities connected by one of the most fundamental equations in physics and everyday life. Knowing any two allows you to calculate the third.
The Three Core Formulas
Speed Unit Conversion Factors
Average Speed vs Instantaneous Speed
The v = d/t formula always calculates average speed — total distance divided by total time. This is different from instantaneous speed, which is the speed at a specific moment.
Why Average Speed Matters
If you drive 100 miles in 2 hours, your average speed is 50 mph — even if you stopped for fuel, sat in traffic at 0 mph for 15 minutes, and briefly hit 80 mph on the highway. Average speed summarizes the entire journey. GPS navigation systems calculate ETAs using average speed estimates based on road conditions and historical data.
Average Speed with Multiple Segments
Speed of Sound & Mach Numbers
The speed of sound at sea level and 20°C is approximately 343 m/s (767 mph / 1,235 km/h). This varies with temperature and medium — sound travels at ~4,920 ft/s in water and ~19,685 ft/s in steel. Mach number = object speed ÷ local speed of sound. Above Mach 1 is supersonic; above Mach 5 is hypersonic. The Parker Solar Probe, the fastest human-made object, reached ~163 km/s (Mach 475) at perihelion in 2024.