Engine Displacement Calculator
An engine with an 81 mm bore, 77 mm stroke, and 4 cylinders displaces about 1588 cc, or roughly 1.6 liters. This engine displacement calculator turns three numbers you can read off a spec sheet or measure yourself, the cylinder bore diameter, the piston stroke length, and the number of cylinders, into the total swept volume of the engine. Displacement is the combined volume every piston moves through in one full stroke, and it is the single figure most people mean when they call an engine a 2.0 liter or a 350 cubic inch motor. Enter your measurements in millimeters or inches, and the tool returns the total displacement in the natural unit for your input, plus a liter figure and a cubic inch or cc cross value so you can compare metric and imperial specs side by side. It also reports the volume of a single cylinder, which is useful when you are checking a rebuild or comparing bore and stroke changes.
Quick answer
Engine displacement is the total volume swept by all pistons as they travel from bottom dead center to top dead center once.
What this tells you
- •Engine displacement is the total volume swept by all pistons as they travel from bottom dead center to top dead center once.
- •The formula is V = (pi / 4) times bore squared times stroke, times the number of cylinders.
- •Bore is the internal diameter of a cylinder, and stroke is the distance the piston travels inside it.
- •Metric inputs in millimeters give cubic centimeters (cc), which divided by 1000 gives liters.
- •Imperial inputs in inches give cubic inches, the unit used for classic American V8 engine sizes.
- •One cubic inch equals 16.387 cc, so a 350 cubic inch engine is about 5.7 liters.
How to Use
- 11. Choose your measurement unit, millimeters for most modern and metric engines or inches for classic imperial specs.
- 22. Enter the cylinder bore, the internal diameter of one cylinder, in your chosen unit.
- 33. Enter the stroke, the full distance one piston travels from the bottom to the top of its cylinder.
- 44. Enter the number of cylinders as a whole number, such as 4, 6, or 8.
- 55. Read the total displacement as the primary result, then check the liters, cross unit value, and per-cylinder volume below it.
How It Works
Formula
Displacement = (pi / 4) x bore^2 x stroke x number of cylindersEach cylinder is treated as a circular cylinder of volume (pi / 4) times the bore diameter squared times the stroke length. The bore is squared because the cross-sectional area of a circle depends on the diameter squared, and the (pi / 4) factor converts that squared diameter into a true circular area rather than a square one. Multiplying the single-cylinder swept volume by the number of cylinders gives the total engine displacement. When bore and stroke are entered in millimeters the raw result is in cubic millimeters, so the tool divides by 1000 to report cubic centimeters. When they are entered in inches the result is already in cubic inches. Liters come from dividing cubic centimeters by 1000, and the metric to imperial conversion uses the exact factor of 16.387064 cubic centimeters per cubic inch.
Calculation note: values are processed in the order shown above, using the current input units.
Worked Examples
A typical 1.6 liter four-cylinder
A single cylinder sweeps (pi / 4) times 81 squared times 77, which is about 396,867 cubic millimeters, or 396.9 cc. Multiplying by 4 cylinders gives roughly 1588 cc. Dividing that by 1000 gives 1.588 liters, the figure a manufacturer would round to a 1.6 liter badge.
A classic 350 cubic inch V8
With a 4 inch bore and 3.48 inch stroke, each cylinder sweeps (pi / 4) times 16 times 3.48, about 43.7 cubic inches. Across 8 cylinders that is roughly 349.8 cubic inches, the famous small block 350 size. Multiplying by 16.387 gives about 5732 cc, or 5.7 liters.
A single-cylinder motorcycle engine
A square engine with equal 100 mm bore and stroke and one cylinder sweeps (pi / 4) times 100 squared times 100, which is 785,398 cubic millimeters, or 785.4 cc. This is a common size for a large thumper single, and the per-cylinder volume equals the total because there is only one cylinder.
A large 3.0 liter six-cylinder
Each cylinder sweeps (pi / 4) times 84 squared times 89.6, about 496,400 cubic millimeters, or 496.4 cc. Across 6 cylinders that totals roughly 2978 cc, which rounds to the 3.0 liter class that many inline-six and V6 engines fall into.
Common Engine Sizes at a Glance
Approximate displacement for well-known bore, stroke, and cylinder combinations.
| Bore | Stroke | Cylinders | Displacement | Liters |
|---|---|---|---|---|
| 81 mm | 77 mm | 4 | 1588 cc | 1.6 L |
| 84 mm | 89.6 mm | 6 | 2978 cc | 3.0 L |
| 100 mm | 100 mm | 1 | 785 cc | 0.79 L |
| 4 in | 3.48 in | 8 | 349.8 cu in | 5.7 L |
| 4.03 in | 3.53 in | 8 | 360 cu in | 5.9 L |
Real engines are usually rounded to a badge value, so a 1588 cc engine is sold as a 1.6 liter and a 349.8 cubic inch engine is called a 350.
Why bore and stroke both matter
Two engines can share the same displacement while having very different characters, and the reason is the balance between bore and stroke. A wide bore with a short stroke is called oversquare, and it lets an engine rev higher and breathe better at speed, which is why many high-performance and sports engines lean this way. A narrow bore with a long stroke is called undersquare, and it tends to build torque lower in the rev range while running at a calmer engine speed.
Because displacement depends on the bore squared but on the stroke only to the first power, a small increase in bore adds more volume than the same increase in stroke. Boring out a cylinder during a rebuild is one common way to bump displacement, and this calculator lets you test how a new bore or stroke changes the total before you commit to any machining.
Displacement is not the whole story of engine output. Forced induction from a turbo or supercharger, valve timing, compression ratio, and fuel system all shape how much power a given displacement makes. Still, swept volume remains the baseline number that sizes an engine and sets rough expectations for torque and power, which is why it appears on almost every spec sheet.
Common mistakes
- Confusing bore radius with bore diameter. The bore is the full internal diameter of the cylinder, not the radius, and using the radius will give a result four times too small.
- Mixing units within one calculation, such as entering bore in millimeters and stroke in inches. Pick one unit for both measurements and set the selector to match.
- Forgetting to multiply by the number of cylinders. A single-cylinder figure is only a fraction of a multi-cylinder engine's total displacement.
- Entering a non-whole cylinder count. Cylinders come in whole numbers, so a value like 4.5 is not valid and the tool returns no result.
- Assuming displacement alone predicts power. Two engines of the same size can make very different power depending on tuning, aspiration, and design.
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