Natural Gas Pipe Sizing Guide

A gas meter.

Most people think that any natural gas pipe can be used for gas. This certainly isn’t the case. The size of the pipe dictates the amount of gas that can pass along the pipe. It’s also worth noting that the longer the pipe, the lower the flow (be aware that the flow of gas is measured in BTUs (British Thermal Units) per hour. If you’re going to be working with natural gas it’s important to be familiar with the sizes of natural gas pipes and the amount of gas that can pass along them for different lengths.

Nominal Size

The nominal size of the natural gas pipe is actually the exterior size. This is generally used as a reference for the pipe, although the interior size of the pipe is less. For instance, pipe with a nominal size of one inch will have an interior size of just under ½ inch (actually .49 inches).

Pipe Length

The length of the pipe will have a deep influence on the amount of gas that can flow through it. Where a pipe has a nominal size of one inch, the flow will be 547 BTUs for a 10 foot length of pipe, but only 100 for a 300 foot length of pipe. When making your calculations these need to be taken into account. The longer the run of your pipe, the lower the flow of your natural gas.


Most natural gas pipes run up to a nominal size of four inches, although you can get pipe that’s up to eight inches in diameter. When you see the flow for natural gas in pipes, these don’t refer to copper pipes. The specification for these is going to be different, with different figures.

Obviously, the greater the nominal size of natural gas pipes, the greater the gas flow through the pipes. With an 8-inch pipe you’ll have 141,832 BTUs in a 10-foot pipe. For a 150-foot pipe that will be reduced to 36,621. That’s much less, but a great deal more than you’ll find in a pipe with smaller dimensions.

Different sized pipes have different functions. Smaller pipes carry the natural gas to the appliances, for example, and will almost invariably be short runs of pipe. To run a gas cooker, for instance, you need to have good pressure.

Types of Pipe

Different types of pipes can be used as natural gas pipe. This is dependent on the building codes in your area. Steel and copper are the most common materials. Both PVC and polyethylene (PE) pipes can be used for pipes that are buried in the ground outside a building. You’ll also find ductile iron pipes, yellow brass pipes and aluminum pipes that can be used in different situations. Approved flexible connectors are used for connecting gas lines to appliances.

The type and size of the pipe that you use will depend on the amount of BTUs that you need to be delivered to the location. Where possible, cut and thread your own pipe of the correct size to save money.

Now you're set for your natural gas project. You can take pride in knowing you are well versed for your next trip to the hardware store.