Calculator 04 / Engine
Engine Displacement Calculator
Displacement is swept cylinder volume times cylinder count, so bore and stroke matter more than the badge on the engine. Get cubic inch displacement (CID), liters, and cc from bore, stroke, and cylinder count — gas or diesel, any layout.
How this calculator works
Units below default automatically — Metric for non-English pages (or if your device's language is set to one we support), US customary otherwise — and convert automatically if you switch the toggle above the form. Changing language resets to that language's default unless you toggle again.
This is the standard swept-volume formula used across gas and diesel engines alike — each cylinder is treated as a simple cylinder (π/4 × bore² gives cross-sectional area, multiplied by stroke length for volume), summed across all cylinders. It works for inline, V, flat, and any other cylinder layout since geometry per cylinder doesn't depend on how the cylinders are arranged.
Worked example: the Chevrolet 350 small-block
The calculator's default values are a real engine — a 4.000 in bore, 3.480 in stroke V8:
- Bore area = (π ÷ 4) × 4.000² = 0.785398 × 16 = 12.566 in²
- One cylinder = 12.566 × 3.480 = 43.73 in³
- Eight cylinders = 43.73 × 8 = 349.8 in³
- In litres = 349.8 × 0.0163871 = 5.73 L
- In cc = 349.8 × 16.3871 = 5,733 cc
The badge says 350. The geometry says 349.8. Nothing is wrong with either number — manufacturers round displacement to a marketable figure, and they round in whichever direction suits. A 5.7 L badge on the same engine is rounding the other way, from 5.73.
Bore and stroke of engines you can check this against
Every row here was recomputed with the formula above rather than copied from a spec sheet, so you can type any of them into the calculator and see the same figure come back. The gap between the calculated and advertised column is rounding, not error.
| Engine | Bore | Stroke | Cyl | Calculated | Advertised |
|---|---|---|---|---|---|
| Ford 302 / 5.0 Windsor | 4.000" | 3.000" | 8 | 301.6 in³ | 302 CID / 5.0 L |
| Chevrolet 350 small-block | 4.000" | 3.480" | 8 | 349.8 in³ | 350 CID / 5.7 L |
| Ford 351 Windsor | 4.000" | 3.500" | 8 | 351.9 in³ | 351 CID / 5.8 L |
| Chevrolet 383 "stroker" | 4.030" | 3.750" | 8 | 382.7 in³ | 383 CID |
| Chevrolet 454 big-block | 4.250" | 4.000" | 8 | 454.0 in³ | 454 CID / 7.4 L |
| GM Duramax LB7 | 4.055" | 3.897" | 8 | 402.6 in³ | 6.6 L |
| Ford Power Stroke 6.7 | 3.900" | 4.250" | 8 | 406.2 in³ | 6.7 L |
| Cummins 5.9 B-series | 4.020" | 4.720" | 6 | 359.4 in³ | 5.9 L |
| Cummins 6.7 ISB | 4.210" | 4.880" | 6 | 407.6 in³ | 6.7 L |
Cylinder layout never enters the formula. An inline-six and a V6 of the same bore and stroke displace exactly the same, because each cylinder is measured on its own and simply multiplied. That is why the calculator asks for a cylinder count and not an engine configuration.
Bore-to-stroke ratio, and what it tells you
Two engines can displace the same and behave nothing alike. Divide bore by stroke: above 1.00 is oversquare, below is undersquare. It is the single most useful thing the two numbers tell you once you have the displacement.
| Shape | Bore ÷ stroke | Behaviour | Typical of |
|---|---|---|---|
| Strongly oversquare | > 1.20 | Revs freely; peak power high in the range | Petrol performance — Ford 302 is 1.33 |
| Mildly oversquare | 1.05 – 1.20 | Broad, general-purpose power band | Most petrol V8s — Chevrolet 350 is 1.15 |
| Square | ≈ 1.00 | Balanced compromise | Chevrolet 454 is 1.06 |
| Undersquare (long-stroke) | < 1.00 | Torque low down; lower rev ceiling | Diesels — Cummins 5.9 is 0.85 |
This is why a 5.9 L Cummins and a 5.7 L petrol V8 are not comparable engines despite nearly identical displacement. Longer stroke means more leverage on the crank and more piston travel per revolution, which is exactly the trade a diesel wants and a high-revving petrol engine does not.
What an overbore actually adds
Bore is squared in the formula, so boring a block gains displacement faster than the numbers suggest — and it is the reason a rebuilt engine no longer matches its badge. All figures below are a 350 block (3.480 in stroke, 8 cylinders) at successively larger bores.
| Overbore | Bore | Displacement | Gain |
|---|---|---|---|
| Standard | 4.000" | 349.85 in³ | — |
| +0.030" | 4.030" | 355.12 in³ | +5.27 in³ |
| +0.040" | 4.040" | 356.88 in³ | +7.03 in³ |
| +0.060" | 4.060" | 360.42 in³ | +10.57 in³ |
| +0.125" | 4.125" | 372.05 in³ | +22.21 in³ |
Stroke is only multiplied, so it scales in a straight line: the same block stroked from 3.480 to 3.750 in at standard bore gives 377.0 in³. Do both — 4.030 in bore and 3.750 in stroke — and you have 382.7 in³, which is the engine everyone calls a 383. How far a particular block can safely be bored is a question for a machinist with the block in front of them, not for a table.
Displacement unit conversions
| From | To | Multiply by |
|---|---|---|
| Cubic inches (in³ / CID) | Cubic centimetres (cc) | 16.387064 |
| Cubic inches (in³ / CID) | Litres (L) | 0.016387064 |
| Litres (L) | Cubic inches (in³) | 61.0237 |
| Cubic centimetres (cc) | Litres (L) | 0.001 |
| Millimetres (bore/stroke) | Inches | 0.0393701 |
A cc and a millilitre are the same volume, so 5,733 cc and 5.733 L are the same number written twice. Metric bore and stroke figures are usually whole millimetres, which is why a metric-designed engine so rarely lands on a round number of cubic inches.
Where this goes wrong
- Entering the bore as a radius. Bore is the full cylinder diameter. Halving it by mistake divides the answer by four, because bore is squared — this is by far the most common error, and the result is so wrong it is usually obvious.
- Rounding the bore. Bore is squared, so error in it is roughly doubled in the answer. Entering 4.03 instead of 4.030 is harmless; entering 4.0 instead of 4.030 loses 5 in³.
- Using the badge instead of measuring. A "350" that has been bored 0.030 in over is a 355. If you are ordering pistons or filling out a class entry, the block is the authority, not the badge.
- Assuming the advertised litre figure is exact. 5.7 L, 6.6 L and 6.7 L are all marketing roundings of 5.73, 6.60 and 6.65.
- Expecting displacement to predict power. It sets the size of the air pump and nothing else. Compression ratio, cam timing, head flow, fuelling and boost all move power without changing displacement by a single cubic inch.
- Mixing units mid-entry. A bore in millimetres with a stroke in inches produces a number that looks plausible and is meaningless. Switch the toggle rather than converting one field by hand.
Where these numbers come from
Displacement is geometry and the arithmetic is exact. What it does not tell you is output, which is measured under a published test standard rather than derived.
- SAE International — Publishes J1349 and the other test standards a quoted horsepower or torque figure is measured against.
- EPA Vehicles and Engines — Emissions certification data, which is where an engine family's official figures are filed.
Why does my calculated displacement differ slightly from the factory spec?
Factory-published displacement is sometimes rounded, and actual bore/stroke can vary slightly by a few thousandths from nominal spec — small measurement differences compound through the squared bore term.
Does this work for diesel engines too?
Yes — displacement is pure cylinder geometry and applies the same way regardless of fuel type or ignition method.
My engine has been bored over. What do I enter?
Enter the bore it is now, not the bore it left the factory with. A 350 block taken 0.030 in over has a 4.030 in bore and displaces 355 in³, and that is the real engine in front of you — the badge on it is describing a part that no longer exists.
Does cylinder layout — inline, V, flat — change the answer?
No. Each cylinder is measured on its own and multiplied by the count, so an inline-six and a V6 with identical bore and stroke displace identically. Layout affects balance, packaging and firing order, none of which are volume.
Why is bore more sensitive than stroke?
Bore is squared and stroke is not. Increasing bore by 1% raises displacement by about 2%; increasing stroke by 1% raises it by 1%. It is also why mistyping the bore produces a badly wrong answer while mistyping the stroke produces a mildly wrong one.
Maintenance intervals guide
Displacement tells you engine size; it says nothing about service life. For typical oil, coolant, DEF, and fuel filter intervals by duty cycle, see the diesel engine maintenance intervals & fluids guide.
Estimates only, based on the bore and stroke you enter. Use precise measurements for a precise result — small rounding in bore or stroke has an outsized effect since bore is squared in the formula.