What this calculator does
This engine displacement calculator works out the total swept volume of an engine, the figure quoted as "2.0 litre" or "5.7 litre" on a badge or spec sheet, from three measurements: the bore (cylinder diameter), the stroke (how far the piston travels) and the number of cylinders.
Displacement is a pure geometry calculation. Each cylinder is treated as a cylinder in the mathematical sense, swept from the piston at the bottom of its stroke to the top, and that per-cylinder volume is simply multiplied by however many cylinders the engine has. Nothing about fuel, compression or power output enters into it.
The formula
Displacement per cylinder is (π/4) × bore² × stroke, the volume of a cylinder with that diameter and height. Multiplying by the number of cylinders gives total displacement. The result converts automatically to litres (dividing cc by 1,000) and to cubic inches (dividing cc by 16.387), since specifications from different regions use either unit.
| Term | Meaning |
|---|---|
| Bore | The internal diameter of the cylinder, the width the piston travels through. |
| Stroke | The distance the piston travels from the bottom of the cylinder to the top, or vice versa. |
| Displacement | Total swept volume of all cylinders combined, the standard way an engine’s size is described. |
The inputs explained
| Field | What to enter |
|---|---|
| Cylinder bore (diameter) (mm) | Cylinder bore in millimetres, from the manufacturer’s specifications or a measured figure. |
| Piston stroke (mm) | Piston stroke in millimetres, the other dimension needed alongside bore. |
| Number of cylinders | The number of cylinders the engine has, as a whole number. |
When to use it
Checking a manufacturer’s displacement claim
Bore and stroke figures are published for most production engines. Running them through the engine displacement formula checks that the advertised 2.0 litre or 3.5 litre figure matches the underlying geometry.
Estimating displacement after a bore or stroke change
An engine rebuilt with an oversized bore, or a stroker crank with a longer stroke, ends up with a different total displacement. This calculator gives the new figure directly from the revised dimensions.
Converting between litres, cc and cubic inches
Specifications from different markets describe the same engine in litres, cubic centimetres or cubic inches. Working from bore, stroke and cylinder count gives all three at once, rather than converting a single figure by hand.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How total displacement changes with cylinder count at a fixed bore and stroke
The same 86 mm bore and 86 mm stroke, across a range of cylinder counts.
| Cylinders | Total displacement | Total displacement (cc) | Total displacement (cubic inches) |
|---|---|---|---|
| 3 | 1.50 L | 1,499 cc | 91.5 ci |
| 4 | 2.00 L | 1,998 cc | 121.9 ci |
| 5 | 2.50 L | 2,498 cc | 152.4 ci |
| 6 | 3.00 L | 2,997 cc | 182.9 ci |
| 8 | 4.00 L | 3,996 cc | 243.9 ci |
| 10 | 5.00 L | 4,996 cc | 304.8 ci |
How total displacement changes with bore at a fixed stroke and cylinder count
A fixed 86 mm stroke and four cylinders, across a range of bore sizes.
| Bore | Total displacement | Total displacement (cc) | Total displacement (cubic inches) |
|---|---|---|---|
| 60 mm | 0.97 L | 973 cc | 59.4 ci |
| 70 mm | 1.32 L | 1,324 cc | 80.8 ci |
| 80 mm | 1.73 L | 1,729 cc | 105.5 ci |
| 86 mm | 2.00 L | 1,998 cc | 121.9 ci |
| 95 mm | 2.44 L | 2,438 cc | 148.8 ci |
| 110 mm | 3.27 L | 3,269 cc | 199.5 ci |
Questions
What is the engine displacement formula?
Displacement per cylinder equals (π/4) × bore² × stroke, the volume swept by one piston. Multiplying that by the number of cylinders gives the total engine displacement, usually then converted to litres.
How do I calculate engine displacement without bore and stroke?
Bore and stroke are the only two dimensions the calculation needs, so there is no shortcut around them. They are usually published in the engine’s technical specifications, or can be measured directly during a rebuild.
Does this account for the combustion chamber or clearance volume?
No. Displacement is the swept volume only, the difference between the piston at the bottom and top of its stroke. Clearance volume at the top of the cylinder is a separate figure used for compression ratio, not for displacement.
Why do some 2.0 litre engines have different bore and stroke figures?
The same total displacement can be reached with a larger bore and shorter stroke, or a smaller bore and longer stroke. Manufacturers choose that balance for reasons of engine height, rev range and combustion behaviour, not to change the final displacement figure.
For the related compression ratio calculation from bore, stroke and clearance volume, see the engine compression ratio calculator.