Common calibers (Inch/metric equivalents).

US caliber Metric Equivalent Typical Actual Bullet Dia. Common cartridges Notes
.17 4.4 mm 0.172 in .17 Remington, .17 HMR
.177 4.5 mm .177 lead, .175 BB Airgun and BB gun .177 caliber
.20, .204 5 mm 0.204 in .204 Ruger
.22, .218, .219 .220, .221, .222, .223, .224, .225, .226 5.5, 5.56, 5.7 mm 0.223-0.224 in .22 Long Rifle, .223 Remington (5.56mm NATO), 5.7 x 28 mm
.228 none 0.228 in .228 Ackley Magnum Bullets formerly available from Barnes, in heavily constructed 70 and 90 grain weights for medium game use
.24 6 mm 0.243 in .243 Winchester, 6 mm Remington, 6mm plastic (airsoft) BBs
.25 6.35 mm 0.25 in, 6.35 mm .25 ACP, 6.35×16mmSR a.k.a .25 Auto and 6.35 mm Browning
.257 6.5 mm 0.257 in, 6.527 mm .257 Roberts, .25-06 Remington typical 25 cal, not normally called 6.5
.26 6.5 mm 0.264 in, 6.7 mm 6.5 x 55 mm cartridges commonly known as 6.5
.27 6.8 mm, 7 mm 0.277 in, 7.035 mm .270 Winchester, 6.8 SPC not called 7 mm
.28 7 mm 0.284 in, 7.213 mm 7 mm Remington Magnum, 7 x 57 mm commonly called 7 mm
.30 7.62 mm 0.308 in 30-06, .308 Winchester (7.62mm NATO) American “.30 caliber”
.30 7.62 mm 0.311 in .303 British, 7.62×39, 7.62×54R Other “.30 caliber”
.32, .327 7.65 mm 0.309 - 0.312 in .32 ACP, .32 S&W, .327 Federal Magnum .32 caliber handgun cartridges
.32, .325 8 mm 0.323 in .325 WSM, 8 mm Remington Magnum, 8mm plastic (airsoft) BBs .32 caliber rifle cartridges
.338 8.58 mm 0.338 in .338 Lapua, .338 Winchester Magnum .338 Rifle cartridge
.38, .380, .357, .35 9 mm 0.355-0.357 in .38 Special, .380 ACP, .357 Magnum, .35 Remington Generally .357 for revolvers and rifles, .355 in autoloaders
.38 10 mm 0.400 in .38-40 Old black powder cartridge
.40 10 mm 0.400 in .40 S&W, 10 mm Auto
.404 10.25 mm 0.423 in .404 Jeffery
.405 10.75 mm 0.411 in .405 Winchester
.41 10.25 mm 0.410 in .41 Magnum .41 Action Express
.43 11 mm 0.43 in Sl .43 SL large
.44 10.8 mm 0.427 - 0.430 in .44 Magnum
.45 11.45 mm 0.451-0.452 in .45 ACP Handgun .45 calibers, .451 autos and .452 in revolvers
.45 11.6 mm 0.458 in .45-70 Government Most rifle .45 calibers
.454 11.53 mm 0.454 in .454 Casull Once considered a wildcat cartridge, becoming more common
.458, .46 11.6 mm 0.458 in .460 Weatherby, .458 Winchester Magnum
.475, .480 12 mm 0.475 in .480 Ruger, .475 Linebaugh
.50 12.7 mm 0.50 in .50 AE, .500 S&W, .50 Beowulf Desert Eagle, S&W X-Frame, Alexander Arms .50 Beowulf
.50 12.95 mm 0.510 in .50 BMG, 12.7 x 108 mm M2 Browning machine gun and other heavy machine guns, long range rifles typified by Barrett Firearms Manufacturing products
.68 17.5 mm 0.683-0.696 in .689 Caliber Paintball markers Typically .689 Caliber, not called 17.5mm (Not actually a firearm)
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