Last updated: April 2026 · Reviewed by Calculatormatics Editorial Team

Speed Converter

A free speed converter that handles every common unit of velocity: miles per hour (mph), kilometers per hour (km/h), meters per second (m/s — the SI base), knots (nautical miles per hour), feet per second (ft/s), and Mach (multiples of the speed of sound at sea level, 340.29 m/s). Enter a value in any unit and the calculator returns the equivalent in every other instantly. Conversions use exact factors — 1 mph = 0.44704 m/s, 1 km/h = 0.27778 m/s (= 1/3.6), 1 knot = 0.51444 m/s, 1 ft/s = 0.3048 m/s — and the calculator works through m/s as the internal base unit, which guarantees consistent results across unit pairs. The most common conversions: 60 mph ≈ 96.56 km/h; 100 km/h ≈ 62.14 mph; 1 knot ≈ 1.15 mph ≈ 1.85 km/h. Useful for driving abroad (where the speedometer reads in different units), aviation and maritime navigation that use knots, physics homework that needs m/s, ballistics in ft/s, and any cross-system speed arithmetic. Pick a starting unit and enter a value below.

Speed Unit Conversion Formulas

Speed is distance divided by time. Like other physical quantities, speed conversions work by normalizing to a common base unit — in this case, meters per second (m/s), the SI standard. Every speed unit has a fixed ratio to m/s, enabling conversion between any pair of units.

Result = Input × (From factor in m/s / To factor in m/s)

Speed Unit Reference Table

Common Speed Conversions

The mph-to-km/h conversion is the most commonly needed, used when switching between US road speeds (mph) and metric road speeds (km/h). The relationship is:

1 mph = 1.60934 km/h

1 km/h = 0.62137 mph

mph vs. km/h: Country Guide

Road speed limits are displayed in mph in three countries: the United States, the United Kingdom, and Myanmar. The rest of the world uses km/h. When driving internationally or importing a vehicle, knowing how to convert between these two is essential for road safety.

A useful rough approximation: km/h × 0.6 ≈ mph. So 100 km/h ≈ 60 mph. The exact factor is 0.62137, so 100 km/h = 62.1 mph, but 60 mph is close enough for quick estimates.

Knots in Aviation and Maritime

Aircraft airspeed and maritime vessel speed are universally measured in knots (nautical miles per hour). This convention persists because nautical miles and knots align naturally with Earth's coordinate system: 1 nautical mile = 1 arc-minute of latitude. Flight plans, weather forecasts at sea, and ATC communications all use knots worldwide, regardless of whether the country uses metric or imperial on land.

Commercial aircraft cruise at approximately 470–560 knots (860–1,040 km/h or 540–650 mph). Wind speeds in aviation weather reports (METARs) are also given in knots. Runners and cyclists can calculate their performance splits using our Pace Calculator, which converts between speed and pace per mile or kilometer.

Worked Example: Convert 60 mph to km/h

1 mile = 1.60934 kilometers. Since speed is distance per unit time, the miles-to-km factor applies directly:

Step 1: Multiply by the miles-to-km factor
  60 mph × 1.60934 = 96.56 km/h

Step 2: Quick approximation trick
  mph × 1.6 ≈ km/h
  60 × 1.6 = 96 km/h (within 0.6%)

So 60 mph = 96.56 km/h. The same factor works in reverse: divide km/h by 1.60934 to get mph, or multiply by 0.62137.

Frequently Asked Questions