# Cubic inch

A cubic inch (plural: cubic inches) is a non-SI unit of volume, equal to the volume of a cube with sides of one inch.

Cubic inches are still sometimes used as a unit of measurement (in engineering contexts, not household contexts) in the United States, Canada, and United Kingdom, although SI is continuing to gradually displace non-SI usage.

## Notation conventions

The following symbols are used to denote cubic inches:

## Equivalence with other units of volume

1 cubic inch (assuming an international inch) is equal to:

• 0.000578703703703 cubic feet (1 cu ft equals 1,728 cu in)
• about 0.554112552 U.S. fluid ounces
• about 0.004329 U.S. liquid gallons (1 gallon equals 231 cu in exactly (3 in × 7 in × 11 in))
• about 0.00010307 crude barrels (1 barrel equals 42 gallons, or 9702 cu in)
• exactly 0.016387064 litres (1 L is about 61 cu in [exactly 61.0237441 cu in])
• exactly 16.387064 millilitres or cubic centimetres (which in turn are about 0.061 cu in)
• exactly 0.000016387064 cubic metres (1 m³ is about 61,023.75 cu in)

## Uses of the cubic inch

### Electrical box volume

The cubic inch was established decades ago as the conventional unit in the U.S. for measuring the volume of electrical boxes; SI has not yet replaced it for this purpose.

### Engine displacement

The cubic inch was formerly used (until the 1980s) to express the nominal size (displacement) of engines (e.g. 426 HEMI) for new cars, trucks, etc. It is therefore still used for this purpose in the context of the classic-car hobby, auto racing, and so forth. The auto industry nowadays uses SI for this purpose (e.g. 6.1 L HEMI). However, the actual displacement measurements of an engine are still given by many manufacturers in cubic inches (usually along with cc; e.g. the 6.1 L HEMI's published displacement is 370.0 CID/6,059 cc).[1][2][3][4] Some examples of common CID-to-litre conversions are given below. Note that nominal sizes are not always precisely equal to actual sizes. This principle is frequently seen in engineering, tool standardization, etc. (for ease of use) and in marketing (when a big round number sounds more impressive, is more memorable, etc.).

Make (±Division) CID (actual) (nearest 1) CID (nominal) SI (actual) (nearest 0.01) SI (nominal)
Honda, Kawasaki, others something close to 61 CID NA (not marketed in CID) [something close to SI nominal] 1000 cc (= 1.0 L)
Honda, Kawasaki, others something close to 98 CID NA (not marketed in CID) [something close to SI nominal] 1600 cc (= 1.6 L)
Honda, Kawasaki, others; Ford something close to 122 CID NA (not marketed in CID) [something close to SI nominal] 2000 cc (= 2.0 L)
GM (Pontiac, Buick, Oldsmobile, GMC, others) 151 CID NA (not marketed in CID) [something close to SI nominal] 2.5 L
Toyota, Ford, Chrysler, others something close to 183 CID NA (not marketed in CID) [something close to SI nominal] 3.0 L
Ford something close to 244 CID NA (not marketed in CID) [something close to SI nominal] 4.0 L
Ford (Ford, Mercury) [something close to CID nominal] 250 CID 4.10 L 4.1 L
Ford (Ford, Mercury) [something close to CID nominal] 289 CID 4.74 L NA (not marketed in SI)
Ford (Ford trucks and vans) [something close to CID nominal] 300 CID 4.92 L 4.9 L
Ford, GM (Chevrolet) [something close to CID nominal] 302 CID 4.95 L 5.0 L
GM (Chevrolet; others?) 307 CID 307 CID 5.03 L NA (not marketed in SI)
GM (Oldsmobile) 307 CID NA (not marketed in CID) 5.03 L 5.0 L
GM (Chevrolet) 327 CID 327 CID 5.36 L NA (not marketed in SI)
GM (GMC, Chevrolet, Buick, Oldsmobile, Pontiac, others) [something close to CID nominal] 350 CID 5.74 L 5.7 L
Ford (Ford, Mercury) [something close to CID nominal] 351 CID 5.75 L NA (not marketed in SI)
Chrysler (Chrysler, Dodge, Plymouth) [something close to CID nominal] 360 CID 5.90 L 5.9 L
Chrysler (Chrysler, Dodge, Plymouth) [something close to CID nominal] 383 CID 6.28 L NA (not marketed in SI)
AMC, GM [something close to CID nominal] 390 CID 6.39 L NA (not marketed in SI)
GM (Chevrolet) [sometimes 396 CID, sometimes 402 CID] 396 CID 6.49 L NA (not marketed in SI)
GM (Chevrolet; others?) [something close to CID nominal] 400 CID 6.55 L NA (not marketed in SI)
GM (Chevrolet) [something close to CID nominal] 409 CID 6.70 L NA (not marketed in SI)
GM (Pontiac) [something close to CID nominal] 421 CID 6.90 L NA (not marketed in SI)
Chrysler (Chrysler, Dodge, Plymouth) [something close to CID nominal] 426 CID 6.98 L 7.0 L
Ford (Ford, Mercury) [something close to CID nominal] 427 CID 7.00 L 7.0 L
Ford (Ford, Mercury) [something close to CID nominal] 428 CID 7.01 L 7.0 L
Ford (Ford, Mercury) [something close to CID nominal] 429 CID 7.03 L 7.0 L
Chrysler (Chrysler, Dodge, Plymouth) [something close to CID nominal] 440 CID 7.21 L 7.2 L
GM (GMC, Chevrolet) [something close to CID nominal] 454 CID 7.44 L 7.4 L
GM (Buick, Oldsmobile, Pontiac) [something close to CID nominal] 455 CID 7.46 L NA (not marketed in SI)
Ford (Ford [trucks and vans]; Lincoln [cars]) [something close to CID nominal] 460 CID 7.54 L 7.5 L
GM (Cadillac) [something close to CID nominal] 472 CID 7.73 L 7.7 L
GM (Cadillac) [something close to CID nominal] 500 CID 8.19 L 8.2 L
Chrysler (Dodge) 506.5 CID 505 CID 8285 cc 8.3 L
Chrysler (Dodge) 509.8 CID 510 CID 8354 cc 8.4 L

## References

1. 2008 Dodge Charger – Specs & Upgrades. Chrysler. Retrieved on 2008-05-02.
2. Ford Vehicles: Get Specifications F-150. Ford Motor Company. Retrieved on 2008-04-25. “Engine type: 5.4L Triton® SOHC 24-valve V8... Displacement (cu. in.): 330 CID”
3. Chevrolet 2008 Silverado Pickup Truck - Specifications (under engine 'tab'). GM. Retrieved on 2008-04-25. “Engine: Vortec 5.3L Aluminum-Block V8...Displacement (cu. in.): 325”
4. Dodge Specifications. Chrysler LLC. Retrieved on 2008-04-25. “Powertrain: Engine - Displacement - Cubic Inches: 345.0”