Engine Displacement Calculator | Bore x Stroke to Cubic Inches
As the popular saying goes, “there is no replacement for displacement.” But what if that displacement changes due to updated engine parts used to increase the engine’s cylinder bore diameter or crankshaft stroke length? Common machining operations during an engine rebuild, or the addition of performance internal components, such as a rotating assembly with a stroker crank, will change the final displacement value of your engine. As enthusiasts, we are pretty hardcore about knowing every little detail of our builds. An engine bore to stroke calculator is an easy way to determine an engine’s displacement.
Engine Displacement Calculator
Our engine displacement calculator will easily help you calculate engine displacement in both cubic inches and liters by inputting your engine’s bore and stroke, number of cylinders, and any overbore machined into the block. This engine calculator for displacement is helpful in determining total displacement when rebuilding an engine and an overbore is involved or if you are planning to add a stroker crankshaft kit.
Engine Cubic Inches to Liters Calculator
Our cubic inch to liters calculator will help you convert your engine’s total displacement from the classic cubic inch, or CID, measurement to the modern liters of displacement. This engine cubic inch calculator provides displacement in liters and is helpful if you’re looking to confirm your engine’s modern displacement for such purposes as fender badging, custom graphics, etc.
Bore and Stroke Formula for Piston Displacement
Cubic Inch Displacement of One Cylinder: Bore² x 3.14 x Stroke / 4 = CID (single cylinder)
To calculate the bore and stroke of an engine’s cylinder the above equation is used to find the cubic inches of volume that the single cylinder displaces. Once this piston displacement formula calculation has been performed, and rounded as necessary, it is then multiplied by the total number of cylinders that make up the engine to determine the final cubic inch displacement of said engine. This is what our bore and stroke calculator above is doing for you when you insert your engine’s bore (and any additional overbore), stroke, and number of cylinders.
Let's do a sample calculation, assuming a typical bore and stroke for a small block Chevrolet V8. Using the above formula.
- Bore: 4.00 inches
- Stroke: 3.48 inches
- Number of Cylinders: 8
4.00² x 3.14 x 3.48 / 4 = 43.7088 cubic inches (for one cylinder) x 8 = 349.6704 cubic inches - your "350 Chevy." And for liters? Remember L = Cubic Inches ÷ 61.023744, so: 349.6704 ÷ 61.023744 = 5.73L.
Engine Cubic Inches to Liters Conversion Formula
Cubic Inch to Liters: Cubic Inches / 61.023744 = Liters
If all you want to know is the “old school” displacement of a modern engine you can use the following formula: Liters to Cubic Inch: Liters x 61.023744 = Cubic Inch
There are 61.023744 cubic inches (cu. in., CI) in a liter (L). To convert your classic engine’s CID to modern liters designation you simply use the above equation to determine your engine’s displacement in liters. Conversely, if you want to know the cubic inches of a modern engine designated in liters, simply take the liter of displacement, and multiply it by the same value of 61.023744 to obtain the liter to cubic inches conversion value. Our engine size calculator above makes this an easy task.
For example let's take a 5.3L Chevrolet LS engine and find its displacement in cubic inches: 5.3 X 61.023744 = 323.4258432 cubic inches - let's round that to 323 cubic inches.
Let's go with the opposite way now with the venerable Ford 351W and find its displacement in liters: 351 ÷ 61.0237 = 5.7518594723 L, and we'll round that to 5.8 liters.
What Is Engine Bore?
The engine bore of an engine is the bore the piston and connecting rod travel within in a piston-based engine. Usually configured for automotive use in a V-pattern, bores can also be positioned inline, flat horizontally opposed of each other, or even in a W-pattern. The diameter of these cylinder bores is measured either in inches or millimeters, depending upon manufacturer and product timeframe (most engines from the early 1980s and up were advertised in liters, whereas domestic manufacturers had previously used cubic inches to denote engine displacement). The larger the engine bore, the more cylinder volume you have. You will need to know your engine’s bore diameter to determine total displacement when using our engine displacement calculator.
What Is Engine Stroke?
An engine’s stroke is defined as the total distance a piston travels within the cylinder bore of an engine. This travel, from bottom dead center (BDC) to top dead center (TDC) is based upon the measurement from the crankshaft’s pin offset centerline to the crankshaft’s main journal centerline multiplied by two. A stroker engine, such as the popular Chevy 383 stroker kit utilizes a longer stroke. You will find popular crankshafts, such as the SBC 350 crankshaft available in several stroke lengths.
Contrary to popular belief, connecting rod length does not have anything to do with engine stroke. Connecting rod length and piston compression height are normally part of your engine building math to determine final piston deck clearance and are not something an engine displacement calculator requires. Your choice of Chevy 350 pistons or LS pistons, for example, will not affect the crankshaft stroke. Once you have confirmed bore and stroke dimensions you can use our bore and stroke calculator to determine engine displacement.
Oversquare vs Undersquare Engine
The terms square, oversquare, and undersquare, when discussing engine displacement, are specifically referring to the engine’s bore to stroke ratio. The diameter of the engine’s cylinder bore is divided by the piston’s stroke length to provide a ratio. This ratio determines if an engine is square, oversquare, or undersquare. A square engine is one that has an identical bore and stroke, providing a 1:1 ratio. An example of a square engine is Ford’s popular 4.6L Modular engine family with a 90.2mm bore and 90.0mm stroke. But what is an oversquare engine and what are some oversquare engine advantages?
With an oversquare engine, which is one said to be of a shorter stroke, the bore diameter is larger than the piston’s stroke length. Oversquare engines are quite common, as the larger bore diameter provides room for larger valves or multiple valve cylinder head configurations. Furthermore, oversquare engines can achieve higher rpm, so they are often tuned to achieve peak torque at higher rpm ranges. Every small block Chevy iteration, including the 400 SBC stroker kit is an oversquare engine design with a bore to stroke ratio higher than 1:1.
Meanwhile, an undersquare engine is, you guessed it, one where the piston’s stroke length is larger than the bore diameter. Often referred to as a “long stroke” engine, these engines have a bore/stroke ratio lower than 1:1. The smaller bore diameter in these engines mean smaller and/or fewer valves, while the longer piston stroke length lowers the peak torque rpm, however, there are undersquare engine advantages. These longer stroke engines benefit from higher torque. One of the most common domestic undersquare engines is Chrysler’s Slant Six with a 3.41” bore and 4.1” stroke. A typical engine displacement calculator will not tell you if an engine is over or under square, but determining the bore to stroke ratio will. These ratios can be found in the following engine displacement charts we have provided below for popular GM, Ford, and Chrysler engines or for custom engine builds you can use the bore stroke ratio formula mentioned earlier of bore / stroke = bore stroke ratio.
