One cubic inch is exactly 16.387064 cubic centimetres, which makes a cubic inch 0.016387064 of a litre. That is why 350 cubic inches comes out at 5.735 litres rather than a round 5.7, and why a litre figure and a cubic-inch figure for the same engine almost never look like exact equivalents. The tables below run both directions across the displacements that actually turn up.
Where the factor comes from
The inch is defined as exactly 2.54 cm, so a cubic inch is 2.54 cubed — 16.387064 cubic centimetres, exactly, with no approximation anywhere in it. A litre is 1,000 cubic centimetres, so the same conversion in litres is 0.016387064. Going the other way, one litre is 61.0237 cubic inches.
Displacement itself is bore area times stroke times cylinder count, so it is a volume like any other and converts like one. What varies is how the figure is presented: engines are almost always marketed at a rounded litre figure, which is why the badge and the arithmetic rarely agree to the decimal.
Cubic inches to litres and cc
| Cubic inches | Litres | cc |
|---|---|---|
| 61 | 1.000 | 1000 |
| 90 | 1.475 | 1475 |
| 97 | 1.590 | 1590 |
| 122 | 1.999 | 1999 |
| 140 | 2.294 | 2294 |
| 151 | 2.474 | 2474 |
| 170 | 2.786 | 2786 |
| 198 | 3.245 | 3245 |
| 200 | 3.277 | 3277 |
| 225 | 3.687 | 3687 |
| 231 | 3.785 | 3785 |
| 250 | 4.097 | 4097 |
| 258 | 4.228 | 4228 |
| 265 | 4.343 | 4343 |
| 273 | 4.474 | 4474 |
| 289 | 4.736 | 4736 |
| 302 | 4.949 | 4949 |
| 305 | 4.998 | 4998 |
| 318 | 5.211 | 5211 |
| 327 | 5.359 | 5359 |
| 340 | 5.572 | 5572 |
| 350 | 5.735 | 5735 |
| 351 | 5.752 | 5752 |
| 360 | 5.899 | 5899 |
| 383 | 6.276 | 6276 |
| 390 | 6.391 | 6391 |
| 400 | 6.555 | 6555 |
| 409 | 6.702 | 6702 |
| 427 | 6.997 | 6997 |
| 440 | 7.210 | 7210 |
| 454 | 7.440 | 7440 |
| 460 | 7.538 | 7538 |
| 472 | 7.735 | 7735 |
| 500 | 8.194 | 8194 |
Litres to cc and cubic inches
| Litres | cc | Cubic inches |
|---|---|---|
| 1.0 | 1000 | 61.0 |
| 1.2 | 1200 | 73.2 |
| 1.4 | 1400 | 85.4 |
| 1.6 | 1600 | 97.6 |
| 1.8 | 1800 | 109.8 |
| 2.0 | 2000 | 122.0 |
| 2.2 | 2200 | 134.3 |
| 2.4 | 2400 | 146.5 |
| 2.5 | 2500 | 152.6 |
| 2.8 | 2800 | 170.9 |
| 3.0 | 3000 | 183.1 |
| 3.5 | 3500 | 213.6 |
| 3.8 | 3800 | 231.9 |
| 4.0 | 4000 | 244.1 |
| 4.3 | 4300 | 262.4 |
| 4.6 | 4600 | 280.7 |
| 4.8 | 4800 | 292.9 |
| 5.0 | 5000 | 305.1 |
| 5.3 | 5300 | 323.4 |
| 5.7 | 5700 | 347.8 |
| 6.0 | 6000 | 366.1 |
| 6.2 | 6200 | 378.3 |
| 6.6 | 6600 | 402.8 |
| 7.0 | 7000 | 427.2 |
| 7.4 | 7400 | 451.6 |
| 8.0 | 8000 | 488.2 |
Method and precision
One cubic inch is exactly 16.387064 cubic centimetres, derived from the definition of the inch as exactly 2.54 cm. Litre figures are rounded to three decimal places and cubic-inch figures to one, for display only; the converter above uses the unrounded factor. Cubic centimetres are rounded to the nearest whole cc, which is finer than any engine is actually built to.
Why a badge never matches the arithmetic
A marketed displacement is rounded to one decimal place, and the rounding is what makes two figures for the same engine look inconsistent. 350 cubic inches is 5.735 litres, which rounds to 5.7. 351 is 5.752, which rounds to 5.8 — one cubic inch apart in reality and a tenth of a litre apart once rounded. The reverse is worse: a badge reading 5.7 litres can be any of six whole displacements, from 345 to 350 cubic inches.
When ordering parts, work from the cubic-inch figure or the engine code rather than the litre figure — the litre figure is a rounding of the real number, and a rounding cannot be un-rounded.
Engine work is in automotive tools, and anything with a torque figure attached wants torque equipment.