# Speed Converter

Free speed converter. Convert between m/s, km/h, mph, knots, and ft/s instantly with exact conversion factors.

## What this calculates

Convert between common speed units including meters per second, kilometers per hour, miles per hour, knots, and feet per second. All conversions use exact factors based on international definitions.

## Inputs

- **Value** — min 0
- **From** — options: Meters per second (m/s), Kilometers per hour (km/h), Miles per hour (mph), Knots (kn), Feet per second (ft/s)
- **To** — options: Meters per second (m/s), Kilometers per hour (km/h), Miles per hour (mph), Knots (kn), Feet per second (ft/s)

## Outputs

- **Result** — The converted speed value.
- **Conversion** — formatted as text — Step-by-step conversion explanation.

## Details

Speed conversion is important in physics, transportation, aviation, and marine navigation. Different fields use different units: scientists use m/s, drivers use km/h or mph, pilots and sailors use knots.

Key Conversion Factors

- 1 km/h = 1,000/3,600 m/s (exact)

- 1 mph = 0.44704 m/s (exact, based on 1 mile = 1,609.344 m)

- 1 knot = 1,852/3,600 m/s (exact, based on 1 nautical mile = 1,852 m)

- 1 ft/s = 0.3048 m/s (exact)

- 1 mph ≈ 1.60934 km/h

- 1 knot ≈ 1.15078 mph

Common Reference Speeds

- Walking: ~1.4 m/s = ~5 km/h = ~3.1 mph

- Highway driving: ~30 m/s = ~108 km/h = ~67 mph

- Speed of sound in air: ~343 m/s = ~1,235 km/h = ~767 mph

## Frequently Asked Questions

**Q: How do I convert km/h to mph?**

A: Divide the km/h value by 1.609344 to get mph. For example, 100 km/h = 100 / 1.609344 = 62.137 mph. Alternatively, multiply by 0.621371. A quick mental approximation: divide km/h by 1.6.

**Q: What exactly is a knot?**

A: A knot is one nautical mile per hour. One nautical mile is exactly 1,852 meters, so 1 knot = 1.852 km/h = 1.15078 mph. Knots are used in aviation and marine navigation because nautical miles relate directly to degrees of latitude.

**Q: Why do scientists use meters per second?**

A: Meters per second (m/s) is the SI unit of speed. It integrates seamlessly with other SI units in physics equations (force in newtons, energy in joules, etc.), so you don't need conversion factors.

**Q: How fast is the speed of sound in different units?**

A: At sea level and 20°C, the speed of sound in air is approximately 343 m/s = 1,235 km/h = 767 mph = 667 knots. It varies with temperature and medium -- sound travels about 4.3 times faster in water and about 15 times faster in steel.

---

Source: https://vastcalc.com/calculators/conversion/speed-converter
Category: Conversion
Last updated: 2026-04-21