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Compression ratio calculator

How to calculate the Compression Ratio (CR) of your engine
Bartek Bartoszewicz
Tuning Professional

Compression ratio

The compression ratio is very important for the smooth running of an engine.

The ratio between the total displacement and the compression space above the piston (combustion chamber) is the compression ratio. The compression ratio must fit the engine design and fuel! As a rule of thumb, one could say: The higher the octane number of the fuel, the higher the compression ratio can be selected. Too high compression or bad fuel can lead to dangerous knocking. An engine with too low compression loses efficiency and becomes sluggish, since the injected fuel-air mixture cannot be burned properly.

Compression ratio calculator



Piston protrusion:
Thickness of head gasket:


Inner diameter of head gasket:


Capacity of piston:
Capacity of head:





Number of cylinders:




 : 1


 : 1

How to calculate the Compression Ratio (CR) of your engine

Here you can easily calculate the compression of your engine. There are two ways:

  1. Choose your engine code from the drop down menu. All values will be filled out automatically and you can „play around“ with the thickness of the head gasket. Thicker head gaskets will drop your compression ratio.
  2. You can fill all the data manually in the grey fields. This makes sense, if your engine code is not in our list, or if you have made big changes to your engine hardware like other pistons for example.

In order to arrive at the appropriate compression later, it most makes sense to do this via the thickness (gauge) of the head gasket. For this purpose, we offer racing gaskets in 0.1 mm increments for most engines. However, please note that our gaskets are always made to order. So there may be longer delivery times. Additionally, we recommend the use of ARP bolts or studs instead of normal cap screws. The ARP bolts are much more stable against the high combustion chamber pressures and can even be reused.

Which compression should I choose?

We do not want to deal with complicated formulas here. As a rule, when tuning, we want to increase the engine power. In the case of a turbo engine, this means increasing the boost pressure. Up to a certain limit, the original compression can be maintained, only the software is adapted to the higher pressures. But if a different turbocharger comes into play, then the compression must also be adjusted downward. Otherwise, the engine would start knocking very quickly with its stock compression. Modern engines have very good knock control, which then also reduces the ignition should knock occur. The goal, however, should be to prevent this control from becoming active in the first place. So the concept between boost pressure (or filling), fuel quality and compression must fit.

Examples of a good engine concept:

1.8T (20V) engine as used in the Golf MK4 or Audi TT until year 2005:
Garrett GTX28 Turbo, 102 Octan fuel = best CR 8,5:1, max. power output with our ECU tuning: 330 PS (243 kW).

2L TFSI engine as used in the Golf MK5 or Audi A3 until year 2012:
KKK Upgrade Turbo V2 BAR-TEK, 102 Octan fuel = best CR: 9:1, max. power output with our ECU tuning 420 PS (309 kW).

2.5L TFSI engine as used in the Audi RS3 or TTRS:
Garrett GTX 35 Turbo, 102 Octan fuel = best CR 9:1, max. power output with our ECU tuning: 750 PS (552 kW).

You can see from our examples that the best compression is always different. Especially with regard to the final performance. This is also due to the different engine concepts. However, in general it can be said that a lower compression ratio is always better. So if you are not sure, ask us or have your engine professionally gauged. Of course, this is only possible if the cylinder head is not mounted. We can help you with that as well.

Any questions?

We are always happy to help and answer your questions. Call us or chat with us.

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Please leave us a comment.
Nebojsa Pavlovic
22.11.2023, 08:26 Uhr
Ich habe einen Volkswagen Polo 1.4 16V-Motor. Ich habe Nockenwellen mit 12,5 mm (304 Grad) Hub eingebaut. Mich interessiert, welches Komprimierungsverhältnis möglichst niedrig ist.
Alexander Jostes
29.11.2023, 12:23 Uhr
Hallo zusammen! Mein Name ist Alex, und ich hätte eine Frage zum Thema Verdichtung . Ist es möglich bei der Serienleistung , die Verdichtung von 9.5 :1 auf 8.5:1 zu reduzieren ohne das es den Motor in irgend einer Weise beeinträchtigt ? Beim Motor handelt es sich um einen 1.8 T 20V AUM . Lg Alex !
Eduard Meller
07.08.2023, 20:22 Uhr
Ich habe ein AGN mit einem Turbo in einem Beetle verbaut, der Wagen stinkt beim Laufen. Als würde der zu satt eingestellt worden sein. Nun habe ich gelesen, dann AGN eine Verdichtung von 10.5 hat und das ist so gar nicht mit Turbolader kombinierbar... Habt ihr einen Ansatz hier, wie ich meinen Käfer wieder zu einem anständig wagen bekommen kann...
Buzz Murdock
09.02.2023, 04:32 Uhr
Hey so I'm rebuilding a 1.8t awp motor and around my part of the world we have 93 octane fuel at the pumps can't really find any race fuel but I want to bump the compression up some what is the absolute thinnest head gasket I can use? Thank you
10.03.2023, 11:45 Uhr
Moin, änderungen funktionieren immernoch nicht.
Thorsten Platen
16.02.2023, 15:53 Uhr
Moin. In der Liste fehlt der bwj Cupra 1p 2,0 tfsi 240 ps Mit freundlichen Grüßen
icon / general / ico_arrow-rewind
27.03.2024, 13:30 Uhr
Hi! Ist jetzt drin.
23.02.2023, 15:17 Uhr
Funktioniert leider nicht mehr. Weder in Edge noch in Firefox
icon / general / ico_arrow-rewind
04.04.2024, 10:03 Uhr
Hi Daniel! Danke für den Hinweis. Problem wurde zwischenzeitlich gefixt.
Bartek Bartoszewicz
Tuning Professional
His first car was a Polo Mk1 with a 40 Weber twin carburetor and 129 PS (95 kW). His second was an Audi 50. Today Bartek tunes Lamborghinis to 1000 PS (735 kW). Even as a young boy, Bartek disassembled vehicles and put everything back together better. He wrote his high school diploma with oil on his fingers. The trained automotive mechanic with a focus on engines and gearboxes was determined to go into motorsports. In his 10 years in Formal 1, he supervised 73 races, including as engine mechanic for Ralf Schumacher at Toyota. Since 2010, he has dedicated himself fully to his company BAR-TEK® and helps his customers to bring VW and Audi engines to peak performance.
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