Home › Math & Science › Converters › Speed Converter

Speed Converter

Convert mph, km/h, m/s, knots, Mach, and ft/s — instantly

From
To
Result
—
Enter a value to convert
—
mph
—
m/s
—
km/h
—
Knots
—
ft/s
—
Mach
—
Common Speed References

Click any row to load that speed into the converter.

Description m/s km/h mph Knots Mach Scale
Speed Comparison (logarithmic scale)
Conversion Formulas
m/s → km/h km/h = m/s × 3.6 Multiply m/s by 3.6
km/h → mph mph = km/h × 0.621371 Multiply km/h by 0.621
m/s → mph mph = m/s × 2.23694 Multiply m/s by 2.237
Knot definition 1 kn = 0.514444 m/s 1 nautical mile per hour
ft/s → m/s m/s = ft/s × 0.3048 Multiply ft/s by 0.3048
Mach 1 (sea level, 20°C) Mach 1 = 343 m/s Varies with temperature & altitude
6×6 Conversion Factor Matrix

Each cell shows the multiplier to convert row unit → column unit. Click to fill the converter.

How to Use This Calculator

1

Select the Source Unit

Choose m/s, km/h, mph, knots, ft/s, or Mach as your starting unit in the "From" dropdown.

2

Enter the Speed Value

Type any numeric speed. All six units update instantly — no button to press.

3

Read the Conversion

The hero result shows your chosen conversion; all six stat cards show every other unit at once.

Formula & Methodology

km/h to m/s

m/s = km/h ÷ 3.6

Divide kilometers per hour by 3.6 to get meters per second (3.6 = 1000 m/km ÷ 3600 s/h).

mph to km/h

km/h = mph × 1.60934

Multiply miles per hour by the exact conversion factor 1.60934 (one international mile = 1609.344 m).

Mach to m/s

m/s = Mach × 343

Mach 1 ≈ 343 m/s at sea level and 20°C. Speed of sound drops to ~295 m/s at cruising altitude.

About this calculation · Accuracy & Methodology

Key Terms

Meters per Second (m/s)
The SI base unit of speed; used in physics and engineering calculations worldwide.
Kilometers per Hour (km/h)
The standard road speed unit in most countries that use the metric system.
Miles per Hour (mph)
The speed unit used on road signs in the United States and United Kingdom.
Knot (kn)
One nautical mile per hour (1.852 km/h); used in aviation and maritime navigation because one nautical mile equals one arc-minute of latitude.
Mach Number
The ratio of an object's speed to the local speed of sound. Mach 1 = supersonic threshold; Mach 5+ = hypersonic.
Feet per Second (ft/s)
Used in US ballistics, projectile physics, and some engineering contexts.

Real-World Examples

Example 1

US Highway Speed Limit

65 mph

= 104.6 km/h = 29.1 m/s — standard US interstate limit

Example 2

Commercial Jet Cruise

Mach 0.85

= 291.55 m/s = 1,049.6 km/h — Boeing 737 at cruising altitude

Example 3

Ship Navigation Speed

20 knots

= 37 km/h = 23 mph — typical cruise ship speed

Speed Scale Reference

Referencem/skm/hmphMach
Walking pace1.45.03.10.004
City driving13.95031.10.041
Highway driving31.3112.7700.091
High-speed train83.33001860.24
Commercial airliner2509005590.73
Speed of sound3431,2357671.0
Low Earth orbit7,80028,08017,45022.7
Speed of light299,792,458~1.08 billion~671 million~875,000

Speed Units in Transportation and Physics

Why Different Speed Units Persist

Road speed in metric countries uses km/h because it maps neatly to kilometer-based distance signs. The US and UK retained mph because their road infrastructure is mile-based. Aviation adopted knots because one knot equals one nautical mile per hour, and nautical miles correspond directly to arc-minutes of latitude — making navigation on charts far simpler than converting km/h or mph.

Understanding Mach Numbers

The Mach number is not a fixed speed — it varies with temperature, pressure, and medium. At sea level on a standard day (15°C), Mach 1 is about 340 m/s. At cruising altitude (11,000 m) where air temperature is −56°C, it drops to roughly 295 m/s. This is why airliners quote both Mach number and true airspeed (TAS). The Concorde cruised at Mach 2.04, while modern fighter jets routinely exceed Mach 2.

Extreme Speeds

The fastest human-made object is the Parker Solar Probe, which reached approximately 692,000 km/h (430,000 mph, Mach 560) near the Sun in 2024. Meanwhile, the ISS orbits at ~27,600 km/h (Mach 22.4), completing one orbit every 90 minutes. The speed of light in a vacuum — 299,792,458 m/s — is the universe's ultimate speed limit.

Frequently Asked Questions

A knot equals one nautical mile per hour, and a nautical mile equals one arc-minute of latitude. This makes navigation on latitude/longitude charts straightforward without needing to convert units.
The speed of sound (Mach 1) varies with air temperature and pressure. At sea level and 20°C it is about 343 m/s (1,235 km/h). At cruising altitude (~11,000 m) where temperatures are around −56°C, it drops to roughly 295 m/s — so the same Mach number means a lower absolute speed up high.
The Parker Solar Probe reached approximately 692,000 km/h (~430,000 mph, Mach ~560) during a close solar flyby in late 2024, making it the fastest human-made object ever recorded.
Commercial airliners cruise at Mach 0.78 to 0.85, roughly 850–950 km/h (530–590 mph) at an altitude of 35,000–40,000 ft. This is just below the speed of sound to avoid drag-increasing shockwaves.
A quick mental shortcut: multiply mph by 1.6 (exact factor is 1.60934). For example, 60 mph × 1.6 = 96 km/h. Going the other way, multiply km/h by 0.6 to get approximate mph (exact: × 0.621371).
Speed is a scalar — it only has magnitude (e.g., 100 km/h). Velocity is a vector — it has both magnitude and direction (e.g., 100 km/h north). This converter deals with speed (magnitude only).

Real-World Speed Reference

🚶Walking5 km/h · 3.1 mph
🚲Cycling25 km/h · 15.5 mph
🏎️Highway120 km/h · 74.6 mph
✈️Airliner900 km/h · 559 mph
🚀SR-71 Blackbird3,529 km/h · Mach 3
💡Speed of Light299,792 km/s · c

Quick Conversion Table

km/hmphm/sContext
3018.68.3Urban speed limit
5031.113.9City roads
8049.722.2Rural roads
10062.127.8Motorway
13080.836.1German Autobahn
200124.355.6High-speed rail
350217.597.2TGV train
1,235767.3343Speed of sound (Mach 1)