Turbo Size Calculator

How do you determine the correct size for a turbocharger? Its easy, use our Turbo Size Calculator that can help you find the appropriate turbo size based on specific input values. Enter the engine displacement, desired horsepower, boost pressure, volumetric efficiency, and RPM into the calculator to find the turbo size you need.

This calculator estimates the appropriate size of a turbocharger based on engine specifications and desired performance. Fill in the fields below to calculate the turbo size needed for your engine setup.

Enter the engine displacement in cubic inches (ci) — This is the total volume of all cylinders in the engine:

Enter the desired horsepower for the engine — The target power output you want to achieve:

Enter the boost pressure in pounds per square inch (psi) — The additional pressure provided by the turbocharger:

Enter the volumetric efficiency percentage — Represents how effectively the engine breathes, usually between 70-100%:

85%

Enter the engine RPM (Revolutions Per Minute) — The number of revolutions the engine makes in one minute:

How to determine turbo size

Guide For Users

To use the Turbo Size Calculator is simple. Follow these steps:

Enter the Engine Displacement: Input the engine displacement in cubic inches (ci).

Example: 350 ci

Enter the Desired Horsepower: Input the horsepower you aim to achieve.

Example: 500 hp

Enter the Boost Pressure: Input the boost pressure in psi.

More Calculators

Example: 15 psi

Enter the Volumetric Efficiency: Input the efficiency percentage. This is usually around 85%.

Example: 85%

Enter the RPM: Input the engine’s revolutions per minute.

Example: 6000 rpm

After entering these values, click the “Calculate” button to find the turbo size.

What is Turbo Size?

Turbo size means how much a turbo boosts an engine. It is key to spiking engine power by cramming more air in the boom box. This lets the engine burn extra fuel and make extra force. A turbo jack ups air to hike power. Size counts for thrust gains.

Formula

The formula to calculate the turbo size is:

 $Turbo Size = \frac{Air Flow Rate \times (\frac{Volumetric Efficiency}{100}) \times (\frac{RPM}{3456})}{6}$

Where the air flow rate is calculated as:

 $Air Flow Rate = \frac{Desired Horsepower \times 1.45}{Boost Pressure + 14.7}$

Variable	Description
Engine Displacement (ci)	Volume of the engine in cubic inches
Desired Horsepower (hp)	Target horsepower output
Boost Pressure (psi)	Pressure of the turbo boost in psi
Volumetric Efficiency (%)	Efficiency of the engine’s air intake
RPM	Engine revolutions per minute
Air Flow Rate (lb/min)	Rate at which air flows into the engine
Turbo Size (lb/min)	Required size of the turbocharger

How To Calculate – Examples

Example 1

For example your input is:

Input:

Engine Displacement (ci): 400
Desired Horsepower (hp): 600
Boost Pressure (psi): 20
Volumetric Efficiency (%): 90
RPM: 7000

Calculation Steps:

1. Calculate the Air Flow Rate:

 $Air Flow Rate = \frac{600 \times 1.45}{20 + 14.7}$  $= \frac{870}{34.7}$  $\approx 25.07 lb/min$

2. Calculate the Turbo Size:

 $Turbo Size = \frac{25.07 \times (\frac{90}{100}) \times (\frac{7000}{3456})}{60}$  $= \frac{25.07 \times 0.9 \times 2.024}{60}$  $\frac{45.75}{60}$  $\approx 0.76 lb/min$

Result: The required turbo size is approximately 0.76 lb/min.

Example 2

For example your input is:

Input:

Engine Displacement (ci): 300
Desired Horsepower (hp): 450
Boost Pressure (psi): 10
Volumetric Efficiency (%): 85
RPM: 6500

Calculation Steps:

1. Calculate the Air Flow Rate:

 $Air Flow Rate = \frac{450 \times 1.45}{10 + 14.7}$    $= \frac{652.5}{24.7}$  $\approx 26.42 lb/min$

2. Calculate the Turbo Size:

 $Turbo Size = \frac{26.42 \times (\frac{85}{100}) \times (\frac{6500}{3456})}{60}$    $\frac{26.42 \times 0.85 \times 1.88}{60}$    $= \frac{42.34}{60}$  $\approx 0.71 lb/min$

Result: The required turbo size is approximately 0.71 lb/min.

I hope this turbo calc makes turbo size picks easy. Put in what’s known, it does the rest. Handles finding the right cram for your engine boom box just from few clear inputs. Makes turbo choice views quick.

Turbo Size Calculator