What this calculator does
Find your engine's size in cc, liters and cubic inches from three measurements. That size is called displacement. It's the total space the pistons sweep through as they travel from the bottom of their path to the top. It's the number behind a 2.0 L four-cylinder, a 350 cubic inch V8 or a 125 cc motorcycle. You need it to compare engines and to plan a rebuild with a bigger bore or a stroker crank. It's also the starting point for working out compression ratio.
You'll need the bore (the cylinder's width, or diameter), the stroke (how far the piston travels) and the number of cylinders. Enter them in inches or millimeters. The calculator gives the displacement in cubic centimeters, liters and cubic inches. It also shows the volume swept by one cylinder, and the bore-to-stroke ratio.
Where it's used
Why this math matters outside the classroom:
- Engine rebuilds. A rebuilder checks that a V8 with a 4.00 in bore and 3.48 in stroke displaces 349.85 in³, sold as a 350.
- Comparing cars. A buyer learns that an 86 × 86 mm four-cylinder displaces 1,998 cc, which is badged as a 2.0 L.
- Overbore planning. A machinist sees that boring a 4.000 in cylinder to 4.030 in raises a 350 in³ engine to about 355 in³.
- Motorcycle classes. A racer confirms a single-cylinder bike stays under a 125 cc class limit before a big-bore kit.
- Science class. Students use V = πr²h on a 43 mm by 43 mm cylinder and find it sweeps about 62.4 cc.
Grade level and standards: Grade 8; Common Core State Standards for Mathematics 8.G.C.9. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.
How to use it
- Choose whether your bore and stroke are in inches or millimeters.
- Enter the bore (cylinder diameter) and the stroke.
- Enter the number of cylinders.
- Read the displacement in cc, liters and cubic inches, and the volume of one cylinder.
What the inputs mean
- Bore (cylinder diameter)
- Bore is the cylinder's diameter. After an overbore (machining the cylinders wider), use the new size. A 4.000 in bore taken 0.030 in over becomes 4.030 in.
- Stroke
- Stroke is how far the piston travels, from its lowest point (bottom dead center) to its highest (top dead center). It's twice the crankshaft's throw, the offset of the crank pin.
- Number of cylinders
- Count every cylinder that has a piston. Rotary engines don't have a bore and stroke, so they aren't covered.
Formula and method
one cylinder = (π ÷ 4) × bore² × stroke displacement = one cylinder × number of cylinders 1 in³ = 16.387064 cc (exact) 1 L = 1,000 cc
Each cylinder is a cylinder in the math sense too. Its cross-section is a circle with area (π ÷ 4) × bore², where π is pi, the circle constant. The piston sweeps that circle through a height equal to the stroke. Multiply the two, and you get the volume one cylinder sweeps.
Inch measurements give cubic inches (in³), and millimeter measurements give cubic millimeters (1,000 mm³ = 1 cc). An inch is exactly 2.54 cm, so one cubic inch is exactly 2.54³ = 16.387064 cc.
Worked example
A V8 has a 4.00 in bore and a 3.48 in stroke.
- One cylinder: (π ÷ 4) × 4² × 3.48 = 43.731 in³.
- In cubic centimeters: 43.731 × 16.387064 = 716.62 cc.
- All 8 cylinders: 716.62 × 8 = 5,732.98 cc.
- In cubic inches: 43.731 × 8 = 349.85 in³; in liters, 5,732.98 ÷ 1,000 = 5.733 L.
Result: The engine displaces 349.85 cubic inches, which is 5,732.98 cc or about 5.7 L.
Understanding the result
Advertised sizes are rounded. A 349.85 in³ engine is sold as a 350, and a 1,998 cc engine as a 2.0 L. Small differences from a published figure usually come from that rounding.
When the bore is bigger than the stroke, the engine is called oversquare. That leaves room for bigger valves and suits high revs. When the stroke is longer than the bore (undersquare), the engine tends to make more pulling power, or torque, at low speed. Equal bore and stroke is called square.
Assumptions and limitations
- Every cylinder has the same bore and stroke.
- Displacement is only the space the piston sweeps. It doesn't include the combustion chamber above the piston.
- Rotary (Wankel) engines and two-stroke port timing conventions aren't covered.
- Displacement alone doesn't predict power. Power depends on airflow, compression, rpm and tuning.
- For compression ratio, you also need the chamber, gasket, deck and piston volumes. Use the compression ratio calculator for that.
Frequently asked questions
How do I convert cubic inches to liters?
Multiply cubic inches by 16.387064 to get cubic centimeters, then divide by 1,000. A 350 in³ engine is 350 × 16.387064 ÷ 1,000 = 5.74 L.
How much displacement does an overbore add?
Displacement grows with the square of the bore, so a small change in width adds up. Taking a 4.000 in bore V8 with a 3.48 in stroke to 4.030 in adds about 1.5%. That's from 349.85 to about 355.1 in³.
What does cc mean for an engine?
Cubic centimeters, the same as milliliters. In a 125 cc engine, the pistons together sweep 125 mL as they travel one full stroke. And 1,000 cc is 1 L.
What is a stroker engine?
It's an engine fitted with a crankshaft that has a longer throw. That makes the stroke longer, so the displacement grows without changing the bore.
How this calculator is checked
Method: Volume of a cylinder, V = (π/4)·bore²·stroke, times the cylinder count; 1 in³ = 16.387064 cm³ exactly. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.
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