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Speed Converter

Convert speed and velocity units instantly. Supports km/h, mph, m/s, knots, Mach, and more with real-time results.

What is the Speed Converter?

The Speed Converter is a comprehensive tool for converting between different units of speed and velocity. Whether you need to convert kilometers per hour to miles per hour for international travel, or translate scientific measurements from meters per second to everyday units, this converter handles it all instantly.

Speed is measured differently around the world. Most countries use kilometers per hour (km/h) for road speeds, while the United States and United Kingdom commonly use miles per hour (mph). Scientists prefer meters per second (m/s) for precision, and maritime navigation uses knots. This tool bridges all these measurement systems seamlessly.

Privacy First: All conversions are performed entirely in your browser. No data is sent to any server, and no calculation history is stored. Your privacy is fully protected.

Who Should Use This Tool?

Travelers

Convert speed limits when driving in different countries

Students & Educators

Solve physics problems requiring unit conversions

Athletes & Coaches

Compare running speeds in different units

Aviation Enthusiasts

Understand aircraft speeds in knots, Mach, and conventional units

Engineers & Scientists

Quickly convert between metric and imperial systems

Supported Unit Categories

This converter supports 14 speed units across four categories:

Metric Units

International standard measurements

  • Kilometers per hour (km/h)
  • Meters per second (m/s)
  • Kilometers per second (km/s)
  • Meters per minute (m/min)
  • Centimeters per second (cm/s)
  • Millimeters per second (mm/s)

Imperial Units

US and UK measurement systems

  • Miles per hour (mph)
  • Feet per second (ft/s)
  • Feet per minute (ft/min)
  • Inches per second (in/s)
  • Yards per second (yd/s)

Nautical Units

Maritime and aviation standard

  • Knots (kn) - nautical miles per hour

Scientific Units

Advanced physics measurements

  • Mach number - speed of sound ratio
  • Speed of light (c) - universal constant

How to Use the Speed Converter

Converting speed units is simple and takes just a few steps. The tool provides instant results as you type, making it easy to compare values across different measurement systems.

Basic Conversion

1

Enter Your Value

Type the speed you want to convert in the left input field

2

Select Your Units

Click the dropdown to choose your source unit (e.g., km/h)

3

View Results

All converted values appear instantly in the results panel below

Using the Converter Card

The main converter card at the top allows quick conversion between any two units:

  • From field - Enter your value and select the source unit
  • To field - Shows the converted result in your target unit
  • Swap button - Click the arrows to reverse the conversion direction
  • Copy buttons - Click to copy either value to your clipboard

Finding Units Quickly

With 14 units available, the search function helps you find what you need:

1

Click Dropdown

Open any unit selector

2

Type to Search

Enter unit name (e.g., "miles")

3

Select Result

Choose from filtered options

Customizing Your View

You can personalize which units appear in the results:

  • Customize Units - Click to show/hide specific units
  • Decimals - Choose precision from 2 to 8 decimal places, or Auto for smart formatting

Copying Results

  • Single value - Click the copy icon next to any result row
  • All results - Click "Copy All Results" to copy every visible conversion

Features

Real-Time Multi-Unit Display

Unlike basic converters that show only one result at a time, this tool displays all 14 unit conversions simultaneously. As you type a value, every unit updates instantly. This makes it easy to compare speeds across different measurement systems without repeated conversions.

Comprehensive Unit Coverage

The converter includes units for every use case:

  • Everyday speeds - km/h and mph for road travel
  • Scientific precision - m/s, cm/s, and mm/s for laboratory work
  • Navigation - Knots for maritime and aviation
  • Extreme speeds - Mach for supersonic aircraft and c for relativistic physics

Smart Number Formatting

The converter automatically handles extreme values:

  • Very large numbers - Displayed in scientific notation (e.g., 2.998e+8)
  • Very small numbers - Shown with appropriate decimal places
  • Readable formatting - Thousands separated with spaces for clarity

Adjustable Precision

Choose your preferred decimal precision:

  • 2 decimals - Quick approximations
  • 4-6 decimals - Standard accuracy
  • 8 decimals - High precision calculations
  • Auto - Smart precision based on the value

Unit Reference Guide

Not sure what each unit means? The built-in reference panel explains:

  • Unit symbol and full name
  • Relationship to base unit (m/s)
  • Common use cases

Customizable Display

Simplify your view by hiding units you don't need. Uncheck units in the Customize panel to focus on the conversions that matter to you. Your preferences are remembered for future visits.

One-Click Copying

Copy any result instantly with the copy button. The "Copy All" feature lets you grab every visible result at once, formatted with unit symbols for easy pasting into documents or messages.

Frequently Asked Questions

What is the difference between speed and velocity?

In everyday language, speed and velocity are often used interchangeably. Technically, speed is a scalar (just a number), while velocity is a vector (includes direction). For unit conversion purposes, they're treated the same way. This converter works for both.

How do I convert km/h to mph?

Enter your km/h value in the input field and select "km/h" as your source unit. The mph result appears instantly in the results panel. For quick reference: 1 km/h equals approximately 0.621 mph.

What is a knot and why is it used?

A knot equals one nautical mile per hour (approximately 1.852 km/h or 1.151 mph). It's used in maritime and aviation because nautical miles align with latitude degrees, making navigation calculations simpler. One minute of latitude equals one nautical mile.

How fast is Mach 1?

Mach 1 is the speed of sound, which varies with temperature and altitude. At sea level and 20°C, Mach 1 is approximately 343 m/s (1,235 km/h or 767 mph). This converter uses the standard sea-level value.

Note: The actual speed of sound changes based on atmospheric conditions. Higher altitudes and colder temperatures result in lower Mach speeds.

Why do scientists use meters per second?

Meters per second (m/s) is the SI unit for speed, making it consistent with other metric measurements. It simplifies calculations in physics equations where distance (meters) and time (seconds) are the standard units.

How accurate are the conversions?

The converter uses precise conversion factors and can display up to 8 decimal places. For most practical purposes, 2-4 decimals are sufficient. Scientific calculations may require higher precision.

Conversion Accuracy 99.99%

Can I convert negative speeds?

Yes, the converter handles negative values. While speed itself is always positive, velocity can be negative to indicate direction. Negative inputs are converted correctly across all units.

What is the speed of light in different units?

The speed of light (c) is approximately 299,792,458 m/s, which equals about:

  • 1,079,252,849 km/h - kilometers per hour
  • 670,616,629 mph - miles per hour
  • 582,749,918 kn - knots
Universal Constant: The speed of light is the fastest speed possible in the universe and remains constant in a vacuum regardless of the observer's motion.

Why are some results shown in scientific notation?

Very large or very small numbers are displayed in scientific notation (e.g., 2.998e+8) for readability. This prevents long strings of digits and makes extreme values easier to understand.

Example: Instead of displaying 299,792,458, the converter shows 2.998e+8, which means 2.998 × 108.

Is my data saved or shared?

No. All calculations happen in your browser using JavaScript. No data is sent to any server, no history is stored, and no personal information is collected. Your conversions are completely private.

100% Privacy Guaranteed: This tool operates entirely client-side. Your data never leaves your device.
km/h
mph
Metric
1.00000000 km/h
Kilometers per Hour
0.27777778 m/s
Meters per Second
0.00027778 km/s
Kilometers per Second
16.66666667 m/min
Meters per Minute
27.77777778 cm/s
Centimeters per Second
277.77777778 mm/s
Millimeters per Second
Imperial
0.62137119 mph
Miles per Hour
0.91134442 ft/s
Feet per Second
54.68066492 ft/min
Feet per Minute
10.93613298 in/s
Inches per Second
0.30378147 yd/s
Yards per Second
Nautical
0.53995680 kn
Knot
Scientific
0.00080985 Ma
Mach (at sea level)
0.00000000 c
Speed of Light
Enter a value and see all unit conversions instantly
Use the dropdown search to quickly find units
Click Copy All to copy every result at once
Adjust decimal precision from 2 to 8 digits
All calculations are done locally - no data sent to server
Want to learn more? Read documentation →
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