Pipe Size Chart and Dimensions

Are you looking to purchase steel pipes, but you’re unfamiliar terminology is getting in the way? Or maybe you can’t wrap your head around the units you see. Don’t worry. We will cover all the standard terminology. We’ll also talk about the pipe size chart and dimensions to update you. Read till the end to answer all the frequently asked questions regarding sizes!

Pipe size chart

NominalO.D. Inches1608080s & E.H.4040s & Std1010s
1/80.405 0.0950.0950.0680.0680.0490.049
1/40.54 0.1190.1190.0880.0880.0650.065
3/80.675 0.1260.1260.0910.0910.0650.065
1 1/41.660.250.1910.1910.140.140.1090.109
1 1/21.90.2810.20.20.1450.1450.1090.109
2 1/22.8750.3750.2760.2760.2030.2030.120.12
3 1/24 0.3180.3180.2260.2260.120.12
4 1/25  0.355 0.247  
77.625  0.5 0.301  
99.625  0.5 0.342  
1111.75  0.5 0.375  
outside pipes

What are the standard sizes?

A lot of homeowners will encounter difficulty in understanding piping systems and their sizing systems. Luckily it has been standardized in North America. You may be looking to get those natural gas pipes looked at or reinstalled when you move into a new home. Maybe you’re renovating your existing abode. Even if you decide to hire a professional, it helps to get familiar with the standardization system before you get started.


The Nominal Pipe sizes or NPS was developed to maintain uniformity and ease for customers in North America. It was done to standardize the production of pipes of all materials. These apply to the use of all plumbing and gas. The standard is also used for heating oil and other types of piping used in buildings.

In the chart below, you can identify all the standard sizes. To decipher what the units and terminology mean, you’ll need to read further.

Outside North America, the Diameter Nominal system identifies sizes in the metric unit system. But both can be equated with the help of a chart. For instance, DN 80 is equal to NPS 3.

pipes in the ground

How is Size Measured?

You’ll find the terms Nominal and Schedule in the chart, which is the basis for ‘measurement. While NPS refers to the inner diameter in inches, the Schedule refers to the wall thickness. There are usually no other units to denote these measurements. As well as this, OD is an additional measurement that refers to the Outside Diameter.

From the chart, you can easily find that the dimension ‘4 NPS SCH 40’ has an OD of 4.5”. Under the column for SCH 40, you’ll find the wall thickness is 0.237”.

pipe on the ground

It’s important to note that PVC (Polyvinyl Chloride) pipes follow the standard system and can only be bought in these sizes. With materials like CPVC, both NPS and copper tubing systems can be used to design sizes and dimensions.

If you’re looking to work with metals like copper or aluminum, check out these welding resources to get started.

copper pipes
Is Nominal Pipe Size OD or ID?

Another common customer query is whether NPS refers to the Outside Diameter or the Inside Diameter. Technically, it is non-dimensional and is only loosely related to the insider diameter measured in inches. Only with NPS 14 and larger sizes does it start to match the outside diameter in inches.

With NPS 12 and smaller sizes, the OD is greater than the NPS number. This can get confusing, and that’s why it’s best to make use of the chart given above.

Which pipe is ¾ OD?

Assuming the SCH is 40, you can spot that a 3/4 NPS refers to a pipe with an OD of 1.050 inches with the help of a standard pipe size chart. Maybe you’re looking to learn about the unit conversion from metric to Standard American English. Check out this handy resource.

What is the ID of a one-inch pipe?

A one-inch NPS will have an OD of 1.315 inches but several inner diameters depending on the Schedule in question. For a Schedule 40 pipe, the ID will be 0.133″. But for a Schedule 80 of the same NPS, the ID will be 0.179″.

What is the OD of a 16-inch?

NPS 14 and above start to replicate their outer diameter values as mentioned above. So one with NPS 16 will have an outer diameter of 16 inches exactly.

How do I know what size it is?

All of this is great information if you’re looking to purchase some. But what if you’ve got to learn how to determine the size of the ones you already have? Let’s say you would like to set up an iron filter system and know what size yours are. Here’s what you do:

  • Try to read alongside the pipe for a value like NPS 1 SCH 40 to determine the NPS and Schedule value.
  • Suppose you can’t find this anywhere because it is old and numbers have faded away. It’s best to go old school and use the string method.
  • For this, you’ll need a measuring tape or string to measure the circumference.
  • Take the string and wrap it around the pipe and note the point at the ends touch together. Measure this number and note it down as circumference.
  • This value must then be divided by 3.14 to determine the Nominal diameter value.
  • Now you can head to the chart above. Find out which nominal diameter value you arrive at, instantly leading you to the dimension.
  • Additionally, you can also use the string to measure the inner diameter and find the exact number on the chart.
  • Match the ID and OD to find out the resulting NPS value.
construction site with exposed pipe

What is Nominal Bore?

Unfortunately, this isn’t a unit to measure boredom. This term is an alternative to Nominal Pipe Size or NPS. Nominal Bore is just the European version of the term known as Nominal Diameter (DN). To calculate the DN equivalent of NPS (only NPS 5 or above), the NPS is multiplied by 25.

How can we make sure they last long?

Make them last longer.
Soft waterInsulate themNo clogging
Rid them of moistureNo harsh chemicalExtra measures with electrical
two pieces of foam pipe insulation

This is a major concern all homeowners and factory owners have. Fixing and replacing them can prove expensive, especially if they are walled in or underground. Here are a few tips to make sure you don’t have to keep digging to fix them.

  • Keep the water soft – For water pipes, hard water is the single biggest cause of early corrosion. You don’t want those minerals building up inside and clogging the entire system. Reverse Osmosis or RO systems keep the whole water running clean and soft and increase the lifespan of your pipes. It also helps with your washing machine too! Maybe you’re looking for good-quality extension cords or outdoor extension cords by length to get that RO going. Study those guides!
  • Insulate them! – If you’re living somewhere the temperature can drop pretty low, it’s best to keep them insulated. It will ensure they don’t burst and leave you freezing in the shower. Speaking of which, here is a great resource to remodel your bathroom in the best way. They can easily be insulated cheaply with the help of self-adhering foam tape. You can also use insulation caps on exterior valves to beat the freeze!
pipe insulation

Run your sprinkler without a water supply to empty them of any moisture. This will ensure they don’t freeze and burst come wintertime.

  • Reduce the pressure! Not many homeowners are aware that increased water pressure can put a strain on the different elements. It includes joints and valves too. Call over a professional plumber to reduce the water pressure if this is the case.
  • Steer clear of harsh chemicals! Cheap fixes to clean them can be costly in the long run. Chemicals from the store might leave your systems prone to damage that even the plumber can’t fix! Call a plumber early to check the drain and save yourself some extra bucks in the long run. If you’re looking to make some extra bucks, take a look at this handy resource for oil rig workers’ salaries.
  • Don’t clog! Never pour grease or oil down the drain. This will cause major clogging of your drain. Don’t forget to add anything fibrous or starchy to the list. Things like vegetables and pasta should not go down the drain.
  • Take extra care with electrical ones. Much more caution is required with electrical products because one spark can cause a huge fire. PVC is usually used for electrical wires and sometimes has the added feature of being non-corrosive and non-combustible. It’s best to choose durable ones because electrical components won’t be easily changed or repaired without breaking walls or ground. If you’re looking to get more resources on good-quality amp wires, here is a handy resource on gauge wire sizes. It’ll help you choose the best one suitable for your needs.

That’s all, folks! We hope you got familiar with the terminology and how to measure and buy pipes of various sizes in North America. Taking care of them will make sure you don’t run into major leakages and mishaps in the long run. We have many other resources on a mixture of sheet metal thickness and a 2-cycle oil mix. Be sure to check them out!