Ammunition Caliber Converter
Convert between millimeters and inches for bullet calibers with reference chart
Conversion
Millimeters
9 mm
Inches
.354"
Match: .380 ACP
Pistol - Typical bullet weight: 95 gr
Closest Calibers
Complete Caliber Reference
| Caliber | Diameter (mm) | Diameter (in) | Bullet (gr) | Type |
|---|---|---|---|---|
| .22 LR | 5.7 | .224 | 40 | Rimfire |
| .223 Remington / 5.56 NATO | 5.7 | .224 | 55 | Rifle |
| .243 Winchester | 6.2 | .243 | 100 | Rifle |
| 6.5 Creedmoor | 6.5 | .264 | 140 | Rifle |
| .270 Winchester | 7 | .277 | 130 | Rifle |
| 7mm Remington Mag | 7.2 | .284 | 160 | Rifle |
| .30-06 Springfield | 7.8 | .308 | 165 | Rifle |
| .308 Winchester / 7.62 NATO | 7.8 | .308 | 150 | Rifle |
| .300 Win Mag | 7.8 | .308 | 180 | Rifle |
| .338 Lapua Mag | 8.6 | .338 | 250 | Rifle |
| .50 BMG | 12.7 | .51 | 660 | Heavy |
| .380 ACP | 9 | .355 | 95 | Pistol |
| 9mm Luger / 9x19mm | 9 | .355 | 115 | Pistol |
| .357 Magnum | 9.1 | .357 | 158 | Revolver |
| .40 S&W | 10.2 | .4 | 180 | Pistol |
| 10mm Auto | 10.2 | .4 | 180 | Pistol |
| .44 Magnum | 10.9 | .429 | 240 | Revolver |
| .45 ACP | 11.4 | .452 | 230 | Pistol |
| .45 Colt | 11.4 | .452 | 250 | Revolver |
| 12 Gauge (bore) | 18.5 | .729 | 437 | Shotgun |
| 20 Gauge (bore) | 15.6 | .615 | 328 | Shotgun |
Bullet Weight Conversion
1 grain = 0.0648 grams or 1 gram = 15.43 grains
40 grain
= 2.6 grams
115 grain
= 7.5 grams
230 grain
= 14.9 grams
Understanding Caliber Naming
Metric (mm): 9mm, 7.62mm - actual bullet diameter in millimeters.
Imperial (inches): .45, .308 - bullet diameter as decimal inches (no leading zero).
Historical names: Some calibers like .38 Special actually use .357" bullets - the name refers to case diameter, not bullet.
Shotgun gauge: Number of lead balls of bore diameter that equal 1 pound. 12 gauge = 12 balls/pound.