Exhaust Size Calculator
Enter your engine power, choose a single or dual exhaust and whether the engine is turbocharged. The calculator gives the pipe diameter you need and the nearest stock pipe size in inches and millimetres.
- Pipe size from power
- Single or dual
- Turbo or NA
Use crank horsepower. If you only know wheel horsepower, add about 15%.
Exhaust pipe size follows engine power. A pipe needs roughly one square inch of inside area for every 52 hp. That gives about 2.25 inches for 200 hp and 3 inches for 350 hp on a single system. A dual system splits the flow, so each pipe can be smaller.
Exhaust size chart
Pipe diameter in inches. Search for a power.
| Power (hp) | Single | Dual (each) | Turbo single |
|---|---|---|---|
| 150 | 2 | 1.75 | 2.25 |
| 200 | 2.25 | 1.75 | 2.5 |
| 250 | 2.5 | 2 | 2.75 |
| 300 | 2.75 | 2.25 | 3 |
| 350 | 3 | 2.25 | 3.5 |
| 400 | 3.5 | 2.5 | 3.5 |
| 500 | 3.5 | 2.75 | 4 |
| 600 | 4 | 3 | 4.5 |
Dual sizes are for each pipe. Turbo engines usually run a bigger downpipe and single exhaust.
Power and pipe size
Single, naturally aspirated. Slide the power.
The tailpipe in the drawing is drawn to scale for the size the calculator picks.
How to size an exhaust
Power to pipe area. Step through it.
Find the power
Crank hp.
Mandrel-bent pipe keeps its full diameter through bends; crush-bent pipe loses some area at each bend.
Single, dual or true dual
Layouts. Compare them.
One pipe after the collector.
Two pipes from a V engine.
Two pipes joined by an X or H.
An X-pipe or H-pipe between two pipes evens out the pulses and usually adds a little power.
Before buying
Exhaust checks. Tick each item.
Tick each item as you go.
Check local noise limits. A bigger pipe with a straight-through silencer can be much louder.
What you get
Exhaust sizing. Each tile explains one result.
Nearest stock size.
Inches and mm.
hp and kW.
Single or dual.
Turbo or NA.
Too big is not better: gas slows down and you lose torque low in the rev range.
Frequently Asked Questions
No question matches that search.
What size exhaust do I need for 300 hp?
About 2.75 inches single, or 2.25 inches for each pipe of a dual system.
What size exhaust for 400 hp?
About 3 to 3.5 inches single, or 2.5 inches dual.
Does a bigger exhaust add power?
Only if the old pipe was too small. Too big can cost torque.
Is 3 inch exhaust good for a turbo?
Yes, 3 inches suits most turbo cars up to about 350 hp.
How do I size a dual exhaust?
Each pipe needs a bit more than half the area of a single pipe.
Does pipe size change the sound?
Yes, bigger pipes usually sound deeper and louder.
What is mandrel bending?
Bending that keeps the full pipe diameter through the bend.
A pipe that lets the engine breathe
Match the pipe to your power and layout. You keep the low-down torque and free up power at the top end.
More size calculators
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