Bore to CC Engine Displacement Calculator

In 2026, an engine builder in Tulsa stroking a Chevy LS3 from 6.2 L to 7.0 L needs to verify the new crankshaft geometry will yield exactly 427 ci before ordering forged pistons at $1800/set. Plugging 103.25 mm bore, 100.6 mm stroke, 8 cylinders into this calculator returns 6740 cc = 6.74 L = 411 ci — not 427. The error is in the assumed stroke; the right number is 104 mm. That single sanity check saves the build.

Engine displacement as a swept-volume concept dates to Nikolaus Otto's 1876 four-stroke patent in Germany. Otto's original engine displaced about 6.1 L from a single cylinder — bore 162 mm, stroke 250 mm at 180 RPM, producing 3 HP. Sixteen years later Rudolf Diesel in 1892 patented the compression-ignition engine, using even longer strokes (his prototype was bore 150 mm, stroke 400 mm — a B/S ratio of 0.375) because long strokes favoured the heat-engine efficiency Diesel was chasing per Carnot.

Through the early 20th century the cubic-inch convention took root in America (Henry Ford's 1908 Model T was 177 ci), while Europe adopted litres after the metric system's industrial spread. The split persists culturally to this day: motorcycles globally use cc, cars use L, and US muscle cars remain married to ci (350, 396, 454 small/big-blocks, 426 HEMI, 460 Ford). The ISO 4106 standard (Engine displacement measurement, 1990) formalised cm³ as the SI unit but did not force market labelling.

The bore-to-stroke ratio became a tuning religion in the 1960s. Long-stroke engines (B/S < 1) lever cylinder pressure into torque — ideal for trucks, pickups, and pre-EFI muscle. Short-stroke or oversquare engines (B/S > 1) reduce piston speed at high RPM, enabling F1 (Ferrari V12 ratios > 1.4), MotoGP, and modern sportbikes like the Suzuki Hayabusa(81 × 65 mm = 1.246 ratio) to spin past 11,000 rpm with cast-iron-liner durability.

The square engine (B/S = 1.00) became Honda's signature — the K20A (86 × 86 mm = 1998 cc) and B16A (81 × 77.4 mm) are near-square, balancing top-end power for racing with low-end torque for street use. Toyota matched the philosophy in the 2JZ-GTE (86 × 86 mm = 2997 cc). Modern downsized turbo engines have swung undersquare again: the Ford EcoBoost 1.0L 3-cyl is 71.9 × 82 mm = 0.877 ratio, trading high-RPM headroom for emissions cycle-test efficiency at typical 1500-2500 RPM cruise speeds.

Stroker kits turn a standard block into a bigger engine without changing the deck height. A Chevy 350 SBC (4.00 × 3.48 inch = 5736 cc / 350 ci) can be stroked to 3.875 inches yielding 383 ci, or 3.75 inches yielding 377 ci. The aftermarket Eagle and Scat crankshaft catalogues list every viable combination, but every stroker must be verified for piston-to-deck clearance (1.5 mm minimum at TDC), rod-bolt-to-block clearance, and oil-pickup-to-crank interference. This calculator is the first sanity check; CAD modelling and engine simulation (Engine Analyzer Pro, Lotus Engine Simulation) come next.

For rotary engines like Mazda's 13B, the bore-stroke formula doesn't apply. Wankel chambers are computed by epitrochoid geometry: one 13B rotor displaces 654 cc, two rotors = 1308 cc. The FIA equivalence multiplier of 1.5× for sports-car class regulations means a 13B is treated as a 1962 cc engine — the source of decades of paddock debate every time a 787B wins Le Mans (as in 1991, the only Japanese victory until Toyota in 2018).