🏎️ Exhaust Diameter Calculator
Calculate the recommended exhaust pipe diameter for an engine based on horsepower.
What this calculator does
This tool estimates the recommended exhaust pipe inside diameter for an engine, based on its horsepower, using a widely referenced automotive rule-of-thumb sizing formula.
The formula
Total required exhaust cross-sectional area scales approximately linearly with horsepower, using an empirical constant based on maintaining reasonable exhaust gas velocity. That total area is divided among the number of exhaust pipes (e.g. dual exhaust splits it between 2 pipes), and pipe diameter is found from d = 2√(A/π).
This is a widely used approximate automotive sizing guideline, not an exact fluid-dynamics calculation; optimal exhaust diameter also depends on engine RPM range, header design, and desired power characteristics.