WheelSignal

WheelSignal

Results printed from https://wheelsignal.com/engine-displacement-calculator. Nominal estimates; see assumptions below.

Engine displacement calculator

Work out engine size from bore, stroke and cylinder count, in cc, litres and cubic inches.

Displacement from bore and stroke

Engine dimensions
Unit: mm
Unit: mm
Unit: RPM

Unit choices are saved only if you tick the box, in this browser’s local storage. Measurements are never saved or sent anywhere. A shared link carries the inputs after the # in the address, which browsers don’t send to the server.

Results

Enter bore, stroke and number of cylinders, or press Try an example, then Calculate.

How to use the displacement calculator

  1. Enter the cylinder bore and the crankshaft stroke, in millimetres or inches.
  2. Enter the number of cylinders.
  3. Optionally enter an engine speed to see mean piston speed.
  4. Press Calculate. Switching units converts the numbers you’ve entered.

Worked examples

A four-cylinder engine with an 86 mm bore and 86 mm stroke: each cylinder sweeps π ÷ 4 × 86² × 86 = 499.6 cc, so the engine is 1,998 cc (2.00 L), sold as a 2.0-litre.

Bore and strokeBore 86 mm, stroke 86 mm. Drawing proportions follow the bore-to-stroke ratio.swept volumeTDCBDCbore 86 mmstroke 86 mmIllustrative, proportions follow bore ÷ stroke = 1.000

A V8 with a 4.00 in bore and 3.48 in stroke: 8 × π ÷ 4 × 4.00² × 3.48 = 349.8 cubic inches (5.73 L), the classic “350”.

Formulas used

swept volume per cylinder = π ÷ 4 × bore² × stroke displacement = swept volume × cylinders 1 cubic inch = 16.387064 cc (1 in = 25.4 mm exactly) bore ÷ stroke ratio = bore ÷ stroke mean piston speed (m/s) = 2 × stroke (m) × RPM ÷ 60

For the compression ratio of the same engine, use the compression ratio calculator.

Frequently asked questions

What is engine displacement?

The total volume swept by all the pistons as they move from top dead centre to bottom dead centre. It’s a measure of engine size, not of power: two engines of the same displacement can make very different power.

Why does my calculated figure differ from the badge?

Manufacturers round marketing figures. A 1,998 cc engine is sold as a 2.0, and a 349.8 cubic inch V8 as a 350. Small differences can also come from rounding of published bore and stroke.

What does oversquare and undersquare mean?

An oversquare engine has a bore larger than its stroke (bore ÷ stroke above 1); an undersquare one has a stroke longer than its bore; a square engine has them equal. The ratio is one of many design choices and doesn’t by itself say how an engine performs.

How do I work out the size after a rebore or stroker kit?

Enter the new bore and stroke. For example, an overbore of 0.5 mm adds 0.5 mm to the bore diameter. The calculator shows the new displacement; whether a block can be bored that far is a question for an engine builder.

What is mean piston speed?

The average speed of the piston over a revolution: twice the stroke times RPM, divided by 60. Engine designers use it to compare engines of different sizes. It’s shown for information only; this calculator doesn’t give safe RPM limits.

Last updated .