Wait \u2013 wait \u2013 wait! Don\u2019t just skip this story because the word \u201cMath\u201d appears in the title. You may regret not learning some cool ways to use simple middle-school arithmetic and, okay, some high school geometry to learn something new. Trust us, it will be easy stuff.<\/p>\n

Our formulas are easy. Sure, there are dozens of automotive equations that are useful, but they\u2019re also complex and difficult to execute. The most obvious example is the formula for compression ratio. We\u2019re old enough to remember sharpening our pencils, finding an eraser and large legal pad, and spending an hour or two crunching out multiple variations on piston dome, chamber volume, deck height, and head gasket combinations to find an ideal compression ratio. Thankfully, in the 21^{st<\/sup> Century, there\u2019s no reason to waste time doing that. Several free online compression-ratio programs will crunch the numbers for you.<\/p>\n}

The long-hand version of the compression ratio equation is cumbersome. That\u2019s why it\u2019s not in our Top 5, but it doesn\u2019t mean you shouldn\u2019t know how it works. Having tossed out that caveat, we\u2019ll make it easy for you. Performance Trends offers access to a convenient compression ratio calculator that you can download for free. Just click on the Performancetrends.com website, find the \u201cdownloads\u201d button, and look for the compression ratio calculator.<\/p>\n

Short of that, we\u2019d like to think these short-but-sweet equations are worth saving for future reference. We use at least one of these almost every day for technical articles. Some gearheads recoil at the thought of even simple math, but this stuff is elementary and we promise no Ibuprofen will be required to run these numbers.<\/p>\n

#### 1. How to Calculate Engine Displacement<\/h4>\nHow big is it? That\u2019s the classic car guy question, and we can show you how to quickly calculate this based on three simple inputs: bore, stroke, and the number of cylinders. This can be useful, for example, when considering adding a stroker crank.<\/p>\n

Way back in high-school geometry class (assuming you were paying attention and not ogling the cute girl in the second row), the volume of a cylinder is calculated using the formula of an area of a circle (bore) times the length of the cylinder (stroke). As our example, we\u2019ll use the ubiquitous 350ci small-block Chevy that is fitted with a 4.00-inch bore and a 3.48-inch stroke (displacement = bore radius x bore radius x \u03c0 x stroke).<\/p>\n

To do this, you must first calculate the area of the bore by finding the radius of the bore. Half of the diameter is the radius, so in this case, it is 2 inches. Next, multiply that by itself (2 x 2), then multiply that times \u03c0 (3.14159).<\/span><\/p>\n

**Area = Radius x Radius x <\/b>****\u03c0<\/b>**** (or Radius Squared x <\/b>****\u03c0<\/b>****)<\/b><\/p>\n**

*2 x 2 x 3.1416 = 12.5664<\/span><\/i><\/p>\n*

*Now, you are ready to calculate the displacement:<\/span><\/p>\n*

**Displacement = Area x Stroke<\/b><\/p>\n**

**For our example 350 Chevy engine:<\/p>\n**

*12.5664 x 3.48 = 43.73 cubic inches<\/em><\/p>\n*

*All that\u2019s left to do is multiply that volume times the number of cylinders.<\/p>\n*

*43.73 x 8 cylinders = 349.84 cubic inches<\/em><\/p>\n*

*There is also a handy shortcut:<\/p>\n*

**Displacement = Bore x Bore x Stroke x 0.7854 x Number of Cylinders<\/strong><\/p>\n**

**4 x 4 x 3.48 x 0.7854 = 349.8 (rounded to 350)<\/p>\n**

**There\u2019s also an easy way to remember 0.7854 (a simplified constant to convert the bore squared into Pi-R squared.) If you study the four numbers in the upper left-hand quadrant of any hand calculator, you will see these numbers in clockwise sequence. Once you\u2019ve used it a few times, it becomes second nature, and calculating displacement just got really simple.<\/p>\n**

**Area = Radius x Radius x <\/b>**

**\u03c0<\/b>****(or Radius Squared x <\/b>****\u03c0<\/b>****)<\/b><\/p>\n**

*2 x 2 x 3.1416 = 12.5664<\/span><\/i><\/p>\n*

*Now, you are ready to calculate the displacement:<\/span><\/p>\n*

**Displacement = Area x Stroke<\/b><\/p>\n**

**For our example 350 Chevy engine:<\/p>\n**

*12.5664 x 3.48 = 43.73 cubic inches<\/em><\/p>\n*

*All that\u2019s left to do is multiply that volume times the number of cylinders.<\/p>\n*

*43.73 x 8 cylinders = 349.84 cubic inches<\/em><\/p>\n*

*There is also a handy shortcut:<\/p>\n*

**Displacement = Bore x Bore x Stroke x 0.7854 x Number of Cylinders<\/strong><\/p>\n**

**4 x 4 x 3.48 x 0.7854 = 349.8 (rounded to 350)<\/p>\n**

**There\u2019s also an easy way to remember 0.7854 (a simplified constant to convert the bore squared into Pi-R squared.) If you study the four numbers in the upper left-hand quadrant of any hand calculator, you will see these numbers in clockwise sequence. Once you\u2019ve used it a few times, it becomes second nature, and calculating displacement just got really simple.<\/p>\n**