Exhaust Diameter Calculator

If you've ever wondered "what size exhaust pipe do I need for my automobile?", check out this exhaust diameter calculator. Choose the proper exhaust pipe sizes using our exhaust size calculator.

It allows you to determine exhaust diameter by knowing the engine's RPM and the volume of the vehicle's cylinder. It may seem that choosing an exhaust pipe size is a simple task and bigger always means better, but remember that matching the size of the exhaust pipe to the engine plays a key role in maximizing power at the low-end, mid-range, or top-end. Check our horsepower calculator to calculate your engine's power in horsepower.

If you're unsure how to measure an exhaust pipe, our exhaust diameter calculator will do it for you and calculate the diameter of the exhaust pipe based on the wall thickness and the outer diameter of the pipe. You will also learn what is a straight pipe exhaust and find the optimal exhaust diameter from the exhaust pipe size chart.

Exhaust diameter is measured as the internal diameter of an exhaust pipe of a car for optimal performance and exhaust outflow. During calculations, you need to consider the engine’s peak-torque RPM because exhaust diameter affects engine torque. You can easily find this value using RPM calculator.

Having your specific RPM at peak torque in mind, you want to select optimal exhaust pipe sizes. Since you have already determined the cross-sectional area of the tube, we can now calculate the exhaust pipe inside diameter using the formula:

where:

• $D$ – Exhaust diameter;
• $\rm RPM$ – Maximum rotations per minute, RPM at peak torque;
• $V$ – Single cylinder's volume; and
• $\text{88,200}$ – Mathematical constant.

You can use the engine's peak torque RPM to calculate the primary tube's cross-section area:

If you want to easily calculate a cylinder's volume on your own, check out the bore diameter and stroke of your engine. Then, use one of these formulas:

No matter which formula you choose, you should get the same result: the volume of a single cylinder in your engine.

If your engine has multiple cylinders, e.g., six, simply multiply your result by 6 to obtain total engine displacement. You can also use engine displacement calculator to find your engine's size.

You can calculate the exhaust pipe's internal diameter $\rm ID$ if you measure the tube's outer diameter and wall thickness. To calculate the inside diameter, you must subtract from the measured outer diameter $\rm OD$ the total wall thickness $d$ of the pipe (simply multiply wall thickness by 2) or use our exhaust size calculator:

You can quickly calculate the required exhaust pipe size in just a few steps:

1. Enter the RPM of your engine at maximum torque.

2. Enter the cylinder volume. You can look up this in your car's documentation or measure bore and stroke and then use our calculator. You can also enter the total displacement of the engine and the number of cylinders it has to find the volume of a single cylinder.

3. Calculate exhaust diameter using this exhaust size calculator.

If you would like to see how to measure an exhaust pipe, preferably with a caliper or micrometer, and calculate its diameter:

1. Determine the outer diameter of the exhaust pipe.
2. Measure the wall thickness.
3. The calculator with give you the internal diameter.

A straight pipe exhaust is a system where the role of the exhaust pipe is played by a straight pipe. The exhaust pipe belongs to the exhaust system of your car. Just like a chimney in a house, it serves to release the exhaust gases from the vehicle into the air.