Work out engine displacement from bore, stroke and cylinder count — shown in cc, litres and cubic inches together — with an overbore option, a reverse-solve mode that finds a bore, stroke or cylinder count from a target size, a plain cc ↔ ci ↔ L converter, and a carburettor CFM estimate. Enter your own numbers; nothing is looked up and nothing is sent anywhere.
Bore and stroke to displacement
Use this for an oversize rebore. It is added to the bore before the diameter is squared.
Solve for the missing one
Enter the target displacement and the two you know
The box you're solving for is ignored. Handy after a rebore (solve bore from a known stroke and target) or a stroker crank (solve stroke).
Convert a single engine size between cc, cubic inches and litres
Exact factors: 1 in³ = 16.387064 cc, 1 L = 1000 cc = 61.0237440947 in³.
Engine cycle
Carburettor airflow estimate from displacement
About 0.80–0.85 for a mild street engine; toward 1.0 or above for a well-developed one. This is your estimate, not a baked-in figure.
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The matching engine tool
Got your bore and stroke? Get your compression ratio with the compression ratio calculator — it shares the same bore and stroke but works out the static and dynamic ratio rather than the size. For a tank, drum or any general container rather than a cylinder bore, the same πr²h geometry lives in the cylinder & tank volume calculator.
Bore and stroke to displacement
Engine displacement is the total volume the pistons sweep, and it comes straight out of standard cylinder geometry. One cylinder sweeps a volume of Vs = (π ÷ 4) × bore² × stroke, and the whole engine is that times the number of cylinders: D = cylinders × (π ÷ 4) × bore² × stroke. The bore is the cylinder diameter and the stroke is how far the piston travels, so this is just the area of a circle multiplied by a height, repeated for each cylinder. This is the engine cc calculation, the bore and stroke formula and the piston displacement formula all at once — the same arithmetic whichever name you have seen it under. Because the bore is squared, a small change in diameter moves the answer more than the same change in stroke, which is why an overbore matters.
If you measure in millimetres the raw product is in cubic millimetres; divide by 1000 for cubic centimetres. The Displacement tab takes inches or millimetres, applies an optional overbore to the bore first, and reports cc, litres and cubic inches side by side so you never have to convert by hand. As an engine bore calculator it answers the everyday question — what size is this engine — from the two dimensions you can measure.
cc to cubic inches and litres
Every engine-size question is really one of three units, and moving between them uses exact factors, not rounded ones:
So a cc to cubic inch converter just divides by 16.387064, and the reverse multiplies by it; an engine size cc converter going the other way uses the litre relationship. A 1998 cc engine is 1998 ÷ 16.387064 ≈ 122 cubic inches, about 2.0 litres. The converter tab does any direction. Below is a small computed engine litres to cubic inches chart for common sizes — every figure here is calculated from the factors above, not copied from a table.
Litres to cubic inches and cc — computed from the exact factor 1 L = 61.0237 in³
Litres
Cubic inches
cc
Reverse-solve a bore, stroke or cylinder count
When you already know the displacement you are aiming for, the same formula rearranges to give whichever input you are missing. Solving for the bore:
That is the practical case behind an overbore — how big does the finished bore need to be for a target capacity — or a stroker build, where you fix the bore and find the stroke a longer-throw crank must give. Enter the target and the two dimensions you are keeping and the Reverse-solve tab returns the third.
Carburettor CFM from displacement
A carburettor is sized by the air it can flow, and a reasonable peak-RPM estimate comes from the displacement:
The 3456 is 1728 × 2, because a four-stroke draws a fresh charge only every second crank revolution while a two-stroke fills every revolution, hence the smaller divisor. Volumetric efficiency (VE) is how completely the cylinder fills, defaulting here to 0.85 and editable. Treat the result as a ceiling, not a goal: the common CFM mistake is fitting an oversized carb, which slows the air through the venturi at the low-RPM, part-throttle running where the engine spends its life, blunting throttle response and low-end torque. This is a starting estimate for comparison, not a substitute for matching the carb to the whole combination.
A worked example
A V8 with a 4.00 inch bore and a 3.48 inch stroke:
Eight cylinders ≈ 349.8 cubic inches, about 5732 cc or 5.7 litres.
Bore it 0.030 oversize and the effective bore is 4.030, lifting it to about 355 cubic inches.
At 6000 RPM with VE 0.85: CFM ≈ 350 × 6000 × 0.85 ÷ 3456 ≈ 516 CFM as a peak ceiling.
Terms and spellings
For readers outside the US: “cc” and “cm³” (cubic centimetre or centimeter) are the same thing, “litre” and “liter” are the same, and “cubic inch”, “cu in” and “ci” all mean in³. A motor cc calculator, an engine size calculator and a piston displacement calculator are all asking this one question. The arithmetic is identical regardless of the label; only the units on the answer change.
Term
What it means
Bore
The cylinder's diameter.
Stroke
How far the piston travels between top and bottom.
Swept volume
(π ÷ 4) × bore² × stroke for one cylinder.
Displacement
Swept volume × number of cylinders.
Overbore
Extra diameter from an oversize rebore, added to the bore.
VE
Volumetric efficiency — how completely each cylinder fills.
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Frequently asked questions
What is the engine displacement formula?
Displacement is the swept volume of one cylinder multiplied by the number of cylinders. A single cylinder sweeps Vs = (π ÷ 4) × bore² × stroke, so total displacement D = cylinders × (π ÷ 4) × bore² × stroke. Keep bore and stroke in the same length unit; if you measure in millimetres the raw answer is in cubic millimetres, which divides by 1000 to give cubic centimetres (cc). For example a 4-cylinder with an 81 mm bore and a 77.4 mm stroke works out to about 1595 cc, or 1.6 litres. This calculator does the geometry and shows the same figure in cc, litres and cubic inches together.
How do I convert cc to cubic inches or litres?
The factors are exact: 1 cubic inch = 16.387064 cubic centimetres, 1 litre = 1000 cubic centimetres, and 1 litre = 61.0237440947 cubic inches. So to turn cc into cubic inches you divide by 16.387064, and to turn cubic inches into cc you multiply by it; 350 cubic inches is 350 × 16.387064 ≈ 5735 cc, about 5.7 litres. The converter tab does any of these directions, and because every engine size question is really one of these three units, you can move between an engine quoted in litres, one quoted in cubic inches and one quoted in cc without hunting for a chart.
How do I reverse-solve a bore or stroke after an overbore or a stroker crank?
If you know the displacement you want and two of the three inputs, the third falls out of the same formula. Solving for bore, bore = √(D ÷ (cylinders × (π ÷ 4) × stroke)); solving for stroke, stroke = D ÷ (cylinders × (π ÷ 4) × bore²). That is exactly what you need after boring a block oversize or fitting a longer-stroke crank: enter the target capacity and the dimensions you are keeping, and the reverse-solve mode gives the remaining one. The optional overbore field in the forward mode does the simpler case, adding the overbore to the bore before squaring it.
How do I work out engine cc for a motorcycle or any single-cylinder motor?
It is the same formula with the cylinder count set to one. Enter the bore and stroke in millimetres and set cylinders to 1, and the result in cubic centimetres is the motorcycle or small-engine cc figure people quote. A 95 mm bore and a 92.4 mm stroke single is about 654 cc, for instance. Twins, triples and fours just change the cylinder number; nothing else about the calculation is special to bikes, scooters, karts or generators — displacement is displacement.
How do I estimate carburettor CFM from displacement, and why is bigger not better?
For a four-stroke the airflow estimate is CFM = cubic inches × RPM × volumetric efficiency ÷ 3456, where 3456 is 1728 × 2 because a four-stroke draws a full charge only every second revolution. A two-stroke fills every revolution, so its divisor is 1728. Volumetric efficiency defaults to about 0.85 for a mild street engine and you can raise it toward 1.0 or beyond for a well-developed engine. The classic mistake is fitting too large a carburettor: an oversized venturi kills air speed at the part-throttle, low-RPM running where the engine actually lives, hurting throttle response and low-end torque, so this figure is a peak-RPM ceiling rather than a target to exceed.
Why don't you list displacement for specific engines or vehicle models?
Because those are owner's-manual and brand-specific figures that go out of date, vary by market and year, and add nothing you can trust for the actual engine in front of you, especially once it has been bored or stroked. This tool deliberately ships no engine database and no baked-in model specifications; it computes everything from the bore, stroke and cylinder count you measure or read off your own build sheet, using public-domain cylinder geometry and exact unit-conversion factors. Measure the bore and stroke yourself and the answer reflects your engine, not a generic table.