Convert Length from US Survey Feet to Mils (ft-us to mil)

US Survey Foot to Mil Conversion Formula

Example

Let's convert 5 US Survey Foot (ft-us) to Mil (mil).

Using the formula:

Therefore, 5 US Survey Foot (ft-us) is equal to 60000.12 Mil (mil).

How many us survey feet are in one mil? One Mil (mil) contains 0.000083333166666999999333 US Survey Feet (ft-us) — the inverse of the factor above. Multiplying by 12000.024 takes you from us survey feet to mils; multiplying by 0.000083333166666999999333 brings you back.

Put in words: one us survey foot equals 12000.024 mils, so the us survey foot is the larger unit of this pair. Converting between them never changes the amount of length being measured — only the size of the unit you count it in.

What is a US Survey Foot (ft-us)?

The US Survey Foot is a unit of length historically used for land surveying in the United States.

It is very close in length to the international foot, equaling approximately 1.000002 international feet (ft). The plural form is US Survey Feet.

Where Did the US Survey Foot Come From?

The origin of the US Survey Foot dates back to the Mendenhall Order of 1893. This order defined the relationship between the meter and US customary units.

It established that 1 meter is precisely equal to 39.37 inches. From this relationship, the US Survey Foot was derived, defined as 1200/3937 meters.

This definition differs slightly from the international foot, which was established in 1959 and is defined as exactly 0.3048 meters.

Why Was the US Survey Foot Replaced?

To simplify measurements and prevent confusion, the National Institute of Standards and Technology (NIST) and the National Geodetic Survey (NGS) made a critical change.

They officially retired the U.S. Survey Foot on December 31, 2022.

Surveying and mapping applications in the United States will now use the international foot. This critical change helps unify the National Spatial Reference System (NSRS) and prevents costly errors in large-scale projects.

Why Did This Small Difference Cause Big Problems?

While the difference between a US Survey Foot and an international foot is minuscule—only about two parts per million—it becomes significant over large distances.

For every mile, the discrepancy adds up to approximately 1/8 inch.

This minor error may not be significant for a backyard fence. However, for massive construction projects and infrastructure development, such as bridges that cross state lines, the accumulated error can lead to severe misalignments and costly mistakes.

What is a Mil?

A mil is a tiny unit of length in the imperial system of measurement.

Its most crucial definition is simple: one mil is equal to one-thousandth of an inch (1/1000 or 0.001 inches).

The plural form of the unit is mils.

Where Does the Name 'Mil' Come From?

The name "mil" comes from the Latin word millesimum, which means "thousandth"—a perfect fit for a unit that represents 1/1000th of an inch.

In engineering and manufacturing, especially in the UK, you might also hear a mil referred to as a thou. This nickname helps prevent confusion with metric units, such as the millimeter.

What is a Mil Used For?

The mil measurement is essential in industries where precision is key, even over minimal distances.

To give you some perspective, a human hair is about 2 to 4 mils thick.

This unit is commonly used to specify the thickness or diameter of:

• Thin materials like plastic bags and foils
• Coatings, such as layers of paint or plating
• Paper and cardstock
• Wires and electrical conductors
• Manufacturing tolerances for electronic parts, like printed circuit boards (PCBs)

Mil vs. MM: What's the Difference?

It's crucial not to confuse the imperial mil with the metric millimeter (mm). A millimeter is a much larger unit of measurement.

Here's a simple breakdown of the mil vs. mm conversion:

• 1 mil = 0.0254 mm
• 1 mm = 39.37 mils

As you can see, one millimeter is nearly 40 times larger than one mil.

It is crucial to specify the units used in technical specifications to avoid significant mistakes.

US Survey Foot to Mil Conversion Table

Here are some quick reference conversions from US Survey Foot (ft-us) to Mil (mil):