Engine Displacement Calculator
Engine displacement in cc, litres and cubic inches from bore, stroke and cylinders, with overbore, bore or stroke for a target size and bore/stroke ratio.
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About this toolWhat is the Engine Displacement Calculator?
Displacement is the volume the pistons sweep between bottom and top dead centre, added up over every cylinder. It is the number on the badge, the figure insurers and racing classes use, and the starting point for compression ratio, airflow and fuel sums. Give this calculator a bore, a stroke and a cylinder count and it returns the swept volume in cubic centimetres, litres and cubic inches at once. The default is the classic Chevrolet small block: a 4.000 in bore and 3.480 in stroke over eight cylinders gives 349.85 cu in, or 5,733 cc.
It also runs the sum backwards. Pick "Bore" or "Stroke" and enter a target displacement to find the dimension that hits it, which is how engine builders plan a stroker or a class-legal overbore. An overbore field shows how much a rebore adds, the bore/stroke ratio tells you whether the engine is oversquare or undersquare, and an engine speed field gives mean piston speed. Work in inches or millimetres; switching converts the inputs in place.
- Displacement in cc, litres and cubic inches at once, with per-cylinder volume
- Solve for bore or stroke from a target displacement in any of the three units
- Overbore gain, bore/stroke ratio with oversquare or undersquare label, and mean piston speed
- Inch and millimetre inputs that convert in place, plus a table for other cylinder counts
- Copy results and share a link with your inputs
How to use the Engine Displacement Calculator
- Choose inches or millimetres for bore and stroke.
- Leave "Solve for" on Displacement and enter bore, stroke and the number of cylinders.
- Read total displacement in cc, litres and cubic inches, plus the per-cylinder volume and bore/stroke ratio.
- To plan a rebore, enter the oversize (for example 0.030 in) and read the new displacement and the gain.
- To hit a target size, switch "Solve for" to Bore or Stroke, enter the target in cc, litres or cubic inches, and read the required dimension.
Worked examples
Chevrolet 350 and a 0.030 in overbore
Input
4.000 in bore, 3.480 in stroke, 8 cylinders, 0.030 in overbore
Output
349.85 cu in (5,733 cc); after the overbore 355.12 cu in (5,819 cc)
A thirty-over rebore adds about 86 cc in total, roughly 1.5%. The bore/stroke ratio of 1.149 marks it as oversquare.
Metric four-cylinder
Input
86 mm bore, 86 mm stroke, 4 cylinders
Output
1,998.2 cc, 1.998 L, 121.9 cu in, bore/stroke 1.000 (square)
At 8,000 rpm the 86 mm stroke gives a mean piston speed of 22.9 m/s, high for a production engine.
Bore needed for a 383
Input
Solve for bore, 3.480 in stroke, 8 cylinders, target 383 cu in
Output
Bore 4.185 in
That bore is not practical in a 350 block, which is why the usual 383 recipe keeps a 4.030 in bore and lengthens the stroke to 3.750 in instead.
Stroke for a 2.0 litre with an 81 mm bore
Input
Solve for stroke, 81 mm bore, 4 cylinders, target 2,000 cc
Output
Stroke 97.03 mm
A ratio of 0.83 makes this an undersquare, long-stroke design, typical of engines tuned for low-speed torque and economy.
Background and insight
One cylinder sweeps a cylinder of air with the bore as its diameter and the stroke as its height: V = π/4 x bore² x stroke. Multiply by the cylinder count for the engine total. Because bore is squared, it moves displacement faster than stroke does: a 1% larger bore adds about 2% volume, a 1% longer stroke adds 1%. One cubic inch is exactly 16.387064 cc, since the inch is defined as 25.4 mm.
Advertised sizes are rounded. A Honda K20 is 86 x 86 mm, which works out to 1,998.2 cc and is sold as a 2.0 litre; Ford's 302 measures 301.6 cu in. Rotary and two-stroke engines are counted differently for racing and tax purposes, so check the rulebook if a class limit is at stake.
The bore/stroke ratio says something about character. Oversquare engines (ratio above 1) have room for larger valves and lower piston speed at a given rpm, so they tend to rev; undersquare engines trade that for a compact chamber and strong low-speed torque. Mean piston speed, 2 x stroke x rpm, is a rough check on how hard the rotating parts work: around 20 m/s is common for road engines at their redline, and racing engines run higher with lighter parts.
Common use cases
Engine builds and strokers
Plan the bore and stroke combination that reaches a target size, and see what a rebore adds before the block goes to the machine shop.
Class and registration limits
Check a motorcycle, kart or race engine against a displacement limit after an overbore.
Spec sheet checks
Confirm a quoted engine size from published bore and stroke, and convert between cc, litres and cubic inches.
Teaching engine basics
Show how bore, stroke and cylinder count combine, and why bore has twice the effect of stroke on volume.
Tips and limitations
- Use the finished bore after honing, not the nominal size, if you want the true figure for a built engine.
- Displacement is swept volume only. The clearance volume above the piston matters for compression ratio, not for displacement.
- An overbore also changes the head gasket and piston you need, and every block has a safe limit set by cylinder wall thickness; ask the machinist or check a sonic test.
- Small rounding in bore and stroke moves the answer: 4.00 vs 4.000 in matters if you are within a few cc of a class limit.
- Mean piston speed is a quick comparison number, not a limit. Rod ratio, piston mass and valve train set the real ceiling.
Frequently asked questions
How do you calculate engine displacement from bore and stroke?
Displacement = π/4 x bore² x stroke x number of cylinders. With bore and stroke in centimetres the answer is in cc; in inches it is in cubic inches. A 4.000 x 3.480 in V8 is 0.7854 x 16 x 3.48 x 8 = 349.85 cu in.
How many cc is a cubic inch?
Exactly 16.387064 cc, because an inch is defined as 25.4 mm. So 350 cu in is 5,735 cc and a 2,000 cc engine is 122.0 cu in.
How much displacement does a 0.030 overbore add?
On a 4.000 in bore, 3.480 in stroke V8 it adds 5.3 cu in (about 86 cc), taking a 350 to 355. The gain scales with the square of the bore, so the same oversize adds proportionally a little more on a smaller bore.
What does oversquare mean?
An oversquare engine has a bore larger than its stroke (bore/stroke ratio above 1). It has room for bigger valves and lower piston speed at a given rpm, so it usually revs higher. Undersquare is the opposite; a square engine has equal bore and stroke.
Why is my 1,998 cc engine called a 2.0 litre?
Makers round to one decimal place of a litre for the badge. The exact swept volume depends on the bore and stroke, which are chosen for packaging and tooling, so it rarely lands on a round number.
Does displacement include the combustion chamber?
No. Displacement is the volume swept by the pistons only. The combustion chamber, head gasket and any piston dish make up the clearance volume, which is what the compression ratio calculation adds back.
Is a bigger bore or a longer stroke better for more displacement?
Either works. Bore has the larger effect per millimetre, and a bigger bore allows larger valves, but it is limited by cylinder spacing and wall thickness. A longer stroke needs a new crank and may need shorter rods or different pistons to fit.
Is there an in-depth guide to the Engine Displacement Calculator?
Yes. “Engine Displacement Explained: Bore, Stroke, CC and Cubic Inches” covers the background, how it works, common pitfalls and worked examples. Read the full guide.
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