Why do we call the diameter tape measure a calculator? Because when you wrap it around the circumference of a pipe or a post, it “calculates” the outside diameter instantaneously. It’s a calculator that never slows down because it doesn’t use batteries. The special scale is in inches or millimeters, and it is stretched out by the factor of pi (3.14159). That’s how it does it for you.

Your pipe diameter tape measure is probably the most valuable and simplest tool in your toolbox. It will tell you the outside diameter of a pipeline (or your arm) when you wrap it around the circumference. What if you lost your pipe tape? How would you measure the diameter of a pipe or any round object?

Use a regular tape measure, if it is flexible enough to wrap around the pipe. A carpenter’s tape is made to stay stiff, so it won’t work in this case. Since the end hook won’t let you lay the zero mark against the pipe, you would have to start at the 1 or 2 inch mark. Read the circumference and divide by 3.14159. That’s a lot of trouble.

Use an expensive caliper, transfer the reading to a measuring tape, perhaps, then divide by pi. That’s a clumsy way of doing it.

Get a real expensive micrometer. Since they have a narrow range of measuring (1 inch), it would have to be a certain size to begin with. Then measure the diameter directly. Reading the markings on a micrometer is not the easiest thing to do. You have to read the shaft measurement, then add the tumbler measurement to it.

Lufkin pipe diameter tape measure products are available with different scales. To find the right tape for your needs, here is how to read the codes that are embedded in the SKU numbers.

“P” means that it is a “pi” tape, also known as a diameter tape.

Examples are w606p, w906pd, w606pm, asw616pd, w606pd, w906p.

“D” means that it measures in tenths of an inch. If the “D” were missing, it would measure in 64ths of an inch.

Pi Day is March 14. This year you can help celebrate by answering the question at the bottom.

Pi is the constant ratio of a circle’s circumference to its diameter, no matter what size the circle is. This is useful knowledge when you work with water pipes or oil or gas pipelines, and you need to replace part of it. You can measure the circumference and divide by pi. But there’s an easier way to do that.

Let a Lufkin Diameter tape measure do it for you. You just wrap it around the pipe, and read the diameter. Mathematicians call pi an irrational number, since it goes on for an infinite number of decimal places, but using a diameter tape is a very rational and easy way to find the diameter of a pipe. To see a little video on How to measure the diameter of a pipe, just click here.

This time, we won’t get into the geometry theory of pi that we had in high school. The magic of a pipe diameter tape measure is its simplicity of use. Here are the 3 steps to find the diameter of a pipeline:

Clean the pipe surface. Soil and any other contamination, of course, will make the pipe seem bigger than it really is.

Wrap the diameter tape around it, with the diameter scale visible to you.

Simply read off the tape. This will be the diameter, even though the tape is wrapped around the circumference. That’s all!

Some things to watch for…..Some OD tapes (diameter tapes) are marked in 100ths of an inch. Some are marked in 64ths of an inch. On the 64ths of an inch tape, 32/64 would be 1/2″. 16/64 would be 1/4″. 24/64 would be 3/8″. For convenience, you can use a magic marker to mark some of these common, but confusing measurements.

A diameter tape measure can save you a lot of time and frustration when you want to find the OD (outside diameter) of a pipe, post, or tree. This special tape has the inch scale (or metric scale) stretched out by a factor of pi (3.14159). So, if you wrap it around the pipeline, you will not see the “circumference”. You will see its diameter. You don’t need to divide your answer by 3.14159.

You may be part of a special group of people. We can call this group, FDTU, for “future diameter tape users”. To be in that group, you would have these three qualifications:

After you get one, and learn how to use it, you will use one every week for the rest of your life.

You won’t believe how you ever got along without one.

To help you on this fun journey as a FDTU, let’s find out…

What is a diameter tape.

It is a measuring tape that, when you wrap it around the circumference of a round object (pipeline or tree), it reads the “diameter”. If you would use a regular tape measure, you would have to divide by pi (3.14159) to get the diameter.

How to use a diameter tape.

You simply wrap it around a pipe or shaft, or tree, and have the diameter scale face outward, so you can read it. Make sure you don’t use the other side, because it would give you the circumference.

What you will use it on from now on, to make your life easier.

If you need to replace a car heater hose, but you want to have the new hose on-hand before you remove the old hose, use your diameter tape to measure the diameter (and length) of the old hose. You can do the same routine when replacing plumbing.

My friend owns a marina. He never heard of a diameter tape. I gave him a diameter tape and told him what it was for. He was in the FDTU group, and now he uses this valuable diameter tape measure every day.

Are you in the FDTU Group? Now you know how a simple tape can make your life easier.

If you have to find the length of a pipe, that’s easy. But what about the outside diameter of a pipe? What if you can’t just measure the diameter at the end? What if the pipe doesn’t have its ends exposed. It is part of a piping system, or a pipeline. How can you fine the OD, or outside diameter?

Most people don’t use a pipe diameter measuring tape. The reason is not that they don’t need one. The reason is that they don’t know how powerful it is. They don’t know what it can do for them. Just ask the people who use one every day:

pipe installers

plumbers

pipeline inspectors

pipeline installers and repairmen

HVAC installers

car mechanics

boat mechanics

oil and gas rig workers

sport ball makers

They will tell you this: If you want to know the outside diameter of a pipe or any round object, just wrap the diameter tape around its circumference, and read the diameter on the tape. Simple. You don’t have to divide by pi. The best part of this: Even if the pipe is not perfectly round, the od diameter tape will give you the average outside diameter as if it were perfectly round.