Miles per Hour (mph)

What Is Miles per Hour (mph)?

Miles per hour, written as mph, is a unit that tells you how many miles something travels in one hour. It is a way to measure how fast something is moving. If a car is going 60 mph, it means it could travel 60 miles in one hour if it kept the same speed the whole time.

Miles per hour is mostly used for road speeds, like speed limits, car dashboards, and running or cycling speeds in some countries.

Definition

One mile per hour is the speed of moving exactly one mile in one hour.

• 1 mph means 1 mile in 1 hour.
• 10 mph means 10 miles in 1 hour.
• 60 mph means 60 miles in 1 hour.

In science and engineering, speed is often written as distance divided by time. For miles per hour, the formula is:

Speed in mph = distance in miles / time in hours

If you know how far you went and how long it took, you can find your speed in mph by using this formula.

History / Origin

The word mile comes from an old Roman idea called mille passus, which meant one thousand steps of a Roman soldier. Over many centuries, the mile changed and was standardized in England.

Today, the international mile used in most places that still use miles is defined as exactly 1,609.344 meters.

The hour is an old time unit that comes from dividing the day into 24 equal parts.

Miles per hour became common in English speaking countries when people needed a simple way to measure the speed of horses, ships, trains, and later cars. When motor vehicles became popular, mph was used on road signs and speedometers in countries that already used miles for distance.

Symbol & Abbreviation

The most common way to write miles per hour is:

• mph for miles per hour

Other ways you might sometimes see it written include:

• mi/h using the mile symbol mi and a slash for per hour
• m.p.h. an older style with dots after each letter

Today, mph without dots is the style most people and most devices use.

Current Use Around the World

Miles per hour is mainly used in a few countries that also use miles for road distances. The most important are:

• United States speed limits, car speedometers, some sports
• United Kingdom speed limit signs, car dashboards, road distances
• Canada and others some older or imported cars show mph as a secondary scale

Most countries use kilometers per hour (km/h) on their roads. However, many devices and apps offer both mph and km/h so people can choose the unit they prefer.

You will often see mph used in these situations:

• Speed limit signs on roads in mph countries
• Car and motorcycle speedometers
• Running, cycling, and treadmill displays in some gyms
• Weather reports in some places, for example wind speed given in mph

Example Conversions

To compare mph with other speed units, it helps to know some basic conversion facts.

Miles per hour to kilometers per hour

One mile is exactly 1.609344 kilometers. So:

1 mph ≈ 1.609 km/h (rounded to three decimal places)

General formula:

• km/h = mph × 1.609 (approximate)
• mph = km/h ÷ 1.609 (approximate)

Common examples:

• 30 mph ≈ 48 km/h
• 50 mph ≈ 80 km/h
• 60 mph ≈ 97 km/h
• 70 mph ≈ 113 km/h

Miles per hour to meters per second

In science, speed is often measured in meters per second (m/s). The exact conversion is:

• 1 mph ≈ 0.44704 m/s

Simple formula for quick use:

• m/s ≈ mph × 0.447
• mph ≈ m/s × 2.237

Examples:

• 10 mph ≈ 4.47 m/s
• 30 mph ≈ 13.4 m/s
• 60 mph ≈ 26.8 m/s

Miles per hour to feet per second

Sometimes speed is given in feet per second (ft/s). The exact conversion is:

• 1 mph ≈ 1.4667 ft/s

Examples:

• 15 mph ≈ 22 ft/s
• 30 mph ≈ 44 ft/s
• 60 mph ≈ 88 ft/s

Miles per hour and knots

In ships and planes, speed is often given in knots. One knot is one nautical mile per hour. A nautical mile is longer than a normal mile, so:

• 1 mph ≈ 0.869 knots
• 1 knot ≈ 1.151 mph

Quick reference table

Related Units

Miles per hour belongs to a family of speed units that all compare distance with time. The most common related units are:

• Kilometers per hour (km/h) standard road speed unit in most countries
• Meters per second (m/s) common in science and engineering
• Feet per second (ft/s) sometimes used in physics and ballistics
• Knots (kn) used in aviation and sea travel

Related distance units:

• Mile (mi) distance unit used with mph
• Kilometer (km) distance unit used with km/h

Related time units:

• Second (s)
• Minute (min)
• Hour (h)

FAQs

Is mph the same as mi/h?

Yes. mph and mi/h mean the same thing. Both show miles per hour. mph is just the more common and simpler way to write it.

Which countries use miles per hour?

Miles per hour is mainly used for road speeds in the United States, the United Kingdom, and a few other places that use miles on road signs. Most other countries use kilometers per hour instead.

Why do some cars show both mph and km/h?

Many cars are sold in different countries. To make them easy to use everywhere, their speedometers often show both units. Usually one scale is larger and marked for the main unit of that country, and the other scale is smaller.

How do I quickly change mph to km/h in my head?

A simple trick is to multiply mph by about 1.6. For example, 50 mph times 1.6 is about 80 km/h. To go the other way, divide km/h by 1.6.

Is mph a metric unit?

No. Miles and hours are not part of the modern metric system. The metric speed unit is kilometers per hour (km/h) or meters per second (m/s). mph is part of the older imperial style of units.

Where will I see mph in everyday life?

You will see mph on speed limit signs in mph countries, on car dashboards, in some running or cycling apps, on treadmills in some gyms, and in some weather reports for wind speed.

What is a safe walking speed in mph?

Normal walking speed for many people is around 3 to 4 mph. Fast walking might be around 4 to 5 mph. Running and cycling are usually faster than that.

What is the difference between mph and knots?

Both measure speed, but mph uses normal miles and knots use nautical miles. One knot is about 1.151 mph, and one mph is about 0.869 knots. Knots are common in ships and airplanes, while mph is common on roads.