Engine Displacement Calculator

What is an engine displacement calculator?

An engine displacement calculator works out the total swept volume of an engine from three numbers: the bore (cylinder diameter), the stroke (how far the piston travels), and the number of cylinders. It reports that size in cubic centimetres (cc), litres (L) and cubic inches (ci) at the same time, so you can compare engines whichever unit a spec sheet uses. Mechanics, engine builders, restorers, racers and curious owners use it to confirm an engine’s size, plan a rebuild, or translate a metric figure into the cubic inches stamped on classic American blocks.

Displacement is what people mean by “engine size.” A “2.0 litre” four-cylinder and a “350” V8 are both just statements of total displacement — the combined volume the pistons sweep on one stroke each.

How the engine displacement formula works

The tool uses the cylinder-volume formula applied to every cylinder:

displacement = (π/4) × bore² × stroke × number of cylinders

Each cylinder is treated as a circular bore through which the piston sweeps a height equal to the stroke, so its swept volume is the area of the bore (π/4 × bore²) multiplied by the stroke. Multiplying by the cylinder count gives the whole engine. Here is what every symbol means and the unit it carries:

• bore — the inside diameter of one cylinder. Enter it in millimetres (mm) or inches (in).
• stroke — the distance the piston travels from bottom dead centre to top dead centre, in the same unit as the bore.
• number of cylinders — a whole count (4, 6, 8, and so on).
• π/4 — equals about 0.7854, the constant that turns a squared diameter into a circle’s area.

Units and conversions

With millimetre inputs, the calculator first divides bore and stroke by 10 to get centimetres, then computes (π/4) × bore_cm² × stroke_cm × cylinders, which gives the answer directly in cubic centimetres (cc).

With inch inputs, (π/4) × bore_in² × stroke_in × cylinders gives cubic inches (ci) directly, and the tool converts to cc by multiplying by 16.387064.

The remaining outputs follow from the cc figure:

Output	How it is found
Cubic centimetres (cc)	base result from the formula (mm path)
Litres (L)	cc ÷ 1000
Cubic inches (ci)	cc ÷ 16.387064

Because 1 cubic inch equals exactly 16.387064 cc, those last two rows are exact conversions, not approximations.

Examples

Every example below uses only the formula and conversions above, so you can reproduce each answer by typing the same values into the calculator.

Example 1 — a 2.0 litre four-cylinder (metric, square engine)

Bore 86 mm, stroke 86 mm, 4 cylinders. In centimetres that is 8.6 cm bore and 8.6 cm stroke.

per cylinder = 0.7854 × 8.6² × 8.6 = 0.7854 × 73.96 × 8.6 = 499.6 cc

total = 499.6 × 4 = about 1998 cc ≈ 2.0 L ≈ 121.9 ci

This is a classic “square” engine, where bore equals stroke. The result, about 1998 cc, is why such an engine is sold as a 2.0 L.

Example 2 — a classic 350 V8 (imperial)

Bore 4 in, stroke 3.48 in, 8 cylinders.

total = 0.7854 × 4² × 3.48 × 8 = 0.7854 × 16 × 3.48 × 8 = about 349.8 ci

cc = 349.8 × 16.387064 = about 5733 cc ≈ 5.7 L

The famous small-block “350” comes out to about 349.8 cubic inches, or roughly 5.7 litres — exactly the badge you see on the car.

Example 3 — a 4.7 litre inline-six (metric)

Bore 100 mm, stroke 100 mm, 6 cylinders. That is 10 cm bore and 10 cm stroke.

per cylinder = 0.7854 × 10² × 10 = 0.7854 × 100 × 10 = 785.4 cc

total = 785.4 × 6 = about 4712 cc ≈ 4.7 L ≈ 287.6 ci

A 100 mm square bore and stroke across six cylinders gives about 4712 cc, or 4.7 L — a useful sanity check that bigger bores and more cylinders scale the volume predictably.

Engine size reference: cc, litres and cubic inches

This chart converts common engine sizes between the three units the calculator reports, using cc ÷ 1000 for litres and cc ÷ 16.387064 for cubic inches. Use it to eyeball where a given bore-and-stroke result lands.

Cubic centimetres (cc)	Litres (L)	Cubic inches (ci)	Typical engine
1000	1.0	61.0	small city-car three- or four-cylinder
1998	2.0	121.9	mainstream 2.0 L four-cylinder
2998	3.0	182.9	3.0 L six-cylinder
4712	4.7	287.5	large six or small V8
5733	5.7	349.8	classic 5.7 L “350” V8
6997	7.0	427.0	big-block V8

The litres column rounds to one decimal for display; the cubic-inch column is the exact 16.387064 conversion.

Common uses

The displacement calculator earns its keep anywhere engine size matters:

• Rebuilds and bored blocks — recompute displacement after an overbore (a larger bore) to see the new cc or ci.
• Stroker builds — check how a longer-stroke crankshaft changes total volume before buying parts.
• Cross-unit shopping — turn a metric cc figure into the cubic inches used by older American engines, or vice versa.
• Classic-car identification — confirm whether a block is a 350, 396 or 454 from measured bore and stroke.
• Class and tax brackets — many racing classes, road-tax bands and insurance tiers are set by displacement, so the exact cc matters.
• Education and curiosity — understand why bore, stroke and cylinder count together define engine size.

Tips and common mistakes

• Keep bore and stroke in the same unit. Mixing millimetres for bore and inches for stroke gives nonsense. Pick mm or inches and use it for both.
• Bore is squared, stroke is not. A small increase in bore changes displacement more than the same increase in stroke, because bore is squared in the formula.
• Measure the bore diameter, not the radius. The formula expects the full cylinder diameter; using the radius makes the result four times too small.
• Displacement is per single stroke. It is the volume swept once per cylinder, regardless of whether the engine is two- or four-stroke; do not multiply by two for a four-stroke.
• Do not add the combustion chamber. Displacement excludes the chamber and gasket volume — those belong to the compression-ratio calculation, not the swept volume.
• Rounding is for display. A “2.0 L” engine is often 1998 cc, not exactly 2000; badges round to the nearest tenth of a litre.

Limitations and notes

This calculator returns the theoretical swept displacement from ideal cylinder geometry. It treats each cylinder as a perfect cylinder of the bore diameter and assumes every cylinder is identical, so it does not account for piston dome or dish shape, deck clearance, bore taper, or manufacturing tolerances — real measured displacement can differ slightly. It also does not include the combustion chamber, which is needed for compression ratio but not for displacement. The figure is the same whether the engine runs on a two-stroke or four-stroke cycle, since both sweep the cylinder once per stroke. Everything runs privately in your browser: the bore, stroke and cylinder values you type stay on your device, the math is computed at full precision and only rounded for display, and nothing is uploaded. Treat the result as an accurate engineering estimate of nominal size, and measure the actual bore and stroke for a precise build.

For related work, pair this displacement figure with the compression ratio calculator to size a rebuild, estimate output with the horsepower calculator, or convert top speeds with the speed converter — and find more in the automotive category.