What it does
This converts engine size between cubic centimeters (cc), liters and cubic inches, and works out displacement from the bore, stroke and number of cylinders. Use it to compare a classic V8 rated in cubic inches with a modern engine rated in liters, to check a motorcycle or small-engine cc figure, or to see what a bigger bore or longer stroke does to an engine's size.
How it's calculated
Displacement is the volume all the pistons sweep as they move from the bottom to the top of their stroke. Each cylinder sweeps a cylinder of air:
The unit conversions use exact definitions. The inch is exactly 2.54 cm, so:
Worked example
A four-cylinder engine with an 86 mm bore and an 86 mm stroke: in centimeters that's 8.6 cm × 8.6 cm × 8.6 cm. One cylinder is π ÷ 4 × 8.6² × 8.6 = 499.6 cc. Four of them make 1,998.2 cc, which is sold as a 2.0 L engine.
A classic 350 cubic inch V8 is 350 × 16.387064 = 5,735.5 cc, or 5.7 L.
Reference tables
| Cubic inches | cc | Liters |
|---|---|---|
| 100 | 1,639 | 1.64 |
| 250 | 4,097 | 4.10 |
| 302 | 4,949 | 4.95 |
| 350 | 5,735 | 5.74 |
| 400 | 6,555 | 6.55 |
| 454 | 7,440 | 7.44 |
| 500 | 8,194 | 8.19 |
| Liters | cc | Cubic inches |
|---|---|---|
| 1.0 | 1,000 | 61.0 |
| 1.5 | 1,500 | 91.5 |
| 2.0 | 2,000 | 122.0 |
| 2.5 | 2,500 | 152.6 |
| 3.0 | 3,000 | 183.1 |
| 3.5 | 3,500 | 213.6 |
| 5.0 | 5,000 | 305.1 |
| 6.2 | 6,200 | 378.3 |
Square, oversquare and undersquare
When the bore equals the stroke, an engine is called "square". A bigger bore than stroke is "oversquare", and a longer stroke than bore is "undersquare". The calculator shows the bore-to-stroke ratio so you can see which yours is.
Limitations
- Badges round. A "5.0" might be 4.9 or 5.0 L exactly, and manufacturers round in different ways.
- This is swept volume. It doesn't include the combustion chamber, so it isn't the same as the total cylinder volume used for compression ratio.
- Rotary (Wankel) engines are rated differently and aren't covered by the bore and stroke formula.