Engine displacement calculator
Enter bore, stroke and cylinders, get the engine size.
How do I calculate engine displacement?
Displacement = π ÷ 4 × bore² × stroke × cylinders. A Chevy 350 has a 4.00-inch bore, 3.48-inch stroke and 8 cylinders: 0.7854 × 16 × 3.48 × 8 = 349.8 cubic inches.
How do I convert cubic inches to liters?
Divide by 61.024: 350 cubic inches is 5.7 liters. One cubic inch is exactly 16.387 cc.
How do I convert liters to cubic inches?
Multiply by 61.024: a 5.0-liter engine is 305 cubic inches, and 5.7 liters is 347.8.
How does boring out an engine change the size?
Displacement grows with the square of the bore. Taking a 350 from 4.00 to 4.030 inches ("30 over") gives 355.1 cubic inches.
Can I enter millimeters?
Yes — switch to millimeters and enter the bore and stroke in mm; the answer comes in cc, liters and cubic inches either way.
Worked example: a four-cylinder with an 86 mm bore and stroke
Each cylinder sweeps a column of air, so its swept volume is the area of the bore times the stroke. The bore area is π ÷ 4 × 86² = 5809 mm². Times the 86 mm stroke that is 499557 cubic millimeters, or 499.6 cc, per cylinder. Four cylinders give 1998 cc, which is 2.00 liters or 121.9 cubic inches. The conversion uses 1 cubic inch = 16.387 cc, which follows from 1 inch = 25.4 mm exactly and agrees with the NIST value of 1.638706 × 10⁻⁵ m³.
What do bore-to-stroke ratio, boring and stroking do?
Dividing the bore by the stroke gives a ratio: above 1 the engine is called oversquare, equal to 1 square and below 1 undersquare. The 4.00-inch by 3.48-inch Chevy 350 has a ratio of 1.15, so it is oversquare. Because bore is squared and stroke is not, boring adds more volume per inch than stroking: 4.030 × 3.48 gives 355.1 cubic inches, while keeping the 4.00 bore and lengthening the stroke to 3.75 inches gives 377.0. Combining a 4.030 bore with a 3.75 stroke gives 382.7. Displacement says how much air an engine can move per two crankshaft turns in a four-stroke; it does not by itself give power or compression ratio.
How do I find the bore for a target displacement?
Solve the formula for the bore: bore = √(4 × V ÷ (π × stroke × cylinders)), where V is the total displacement. For a 2-liter four-cylinder with a 90 mm stroke, the volume per cylinder is 500 cc, or 500000 mm³, so the bore is √(4 × 500000 ÷ (π × 90)) = 84.1 mm. Putting that bore back into the formula returns 2000 cc, which confirms the algebra. Real engines use round bore sizes, so the result is usually a little more or less than the target.
Which is bigger, a 5.0-liter or a 302-cubic-inch engine?
A 302 is 4949 cc, or 4.95 liters, while a 5.0-liter is 5,000 cc, or 305 cubic inches. They are essentially the same size, within about 1%. Compare engines in one unit, and compute from bore and stroke when the marketing size is rounded.
Common mistakes with displacement
Mixing units: a bore in millimeters with a stroke in inches gives nonsense, for example 80859 for an 86 mm bore and a 3.48 inch stroke. Using the radius where the formula wants the diameter; the π ÷ 4 factor already allows for halving. Leaving out the cylinder count, or counting only one bank on a V engine. Mistaking rounded marketing sizes for exact ones: a 5.7-liter badge covers a range of exact volumes, so compare engines by computed cc. Confusing displacement with horsepower or with the cylinder’s total volume including the combustion chamber, which is larger than the swept volume.
Sources and related calculators
Sources: geometry of a cylinder (π ÷ 4 × bore² × stroke); NIST Guide to the SI, Appendix B conversion factors (cubic inch = 1.638706 × 10⁻⁵ m³). Related: compression ratio calculator, horsepower calculator, volume calculator and volume converter.