Turbocharger Pressure Ratio Calculator

Purpose and reference point

Calculate turbocharger compressor pressure ratio from boost, ambient pressure, and inlet loss — use the equation to compare setups while keeping the test conditions explicit.

Pressure ratio alone does not determine compressor airflow or efficiency — that condition defines when compressor pressure ratio is comparable with another result.

Traction, grade, wind, temperature, driver input, and control-system intervention remain outside this simplified model — for compressor inlet loss, the page specifically expects pressure drop before the compressor.

When you need to estimate four-stroke engine airflow for carburetor sizing, avoid adding an improvised field here and open the Carburetor CFM.

How the result is derived

In “pressure ratio = compressor outlet absolute pressure ÷ inlet absolute pressure,” the entered measurements must use the reference points described above.

No term beyond gauge boost pressure, ambient absolute pressure, and compressor inlet loss is introduced in “pressure ratio = compressor outlet absolute pressure ÷ inlet absolute pressure.”

Vehicle data needed here

Gauge boost pressure is defined here as compressor outlet pressure above atmosphere — keeping that definition intact requires you to record gauge type, temperature, and whether the value is absolute or relative pressure.

For Ambient absolute pressure, use the quantity described as atmospheric pressure at the operating condition — in the vehicle record, record gauge type, temperature, and whether the value is absolute or relative pressure.

Document Compressor inlet loss as pressure drop before the compressor — this means you should record gauge type, temperature, and whether the value is absolute or relative pressure.

The Brake Hydraulic Line Pressure complements this result by calculating how to estimate ideal brake line pressure from pedal force and system leverage.

Reproducing the sample result

Using the loaded case, the recorded inputs are Gauge boost pressure = 18 psi, Ambient absolute pressure = 14.2 psi, and Compressor inlet loss = 0.4 psi.

For that data set, the calculator returns Compressor pressure ratio = 2.333.

After recording this output, use the Anti-Roll Bar Rate to estimate a simplified solid anti-roll-bar wheel rate.

What a changed result indicates

Compressor pressure ratio answers “Calculate turbocharger compressor pressure ratio from boost, ambient pressure, and inlet loss.”

Measure pressure at the relevant locations — when that condition changes, compare separate calculator runs instead of blending the inputs.

Keep this result separate from the task to calculate idealized braking distance from speed and an effective friction coefficient, which is available in the Vehicle Stopping Distance.

Input and comparison questions