A barrel is one of several units of volume applied in various contexts; there are dry barrels, fluid barrels (such as the UK beer barrel and US beer barrel), oil barrels and so on. For historical reasons the volumes of some barrel units are roughly double the volumes of others; volumes in common usage range from about 100 to 200 litres (22 to 44 imp gal; 26 to 53 US gal).
| US legal cup | pipe | drop (imperial) | pony | imperial minim | fluid scruple | petaliter | hectoliter |
|---|---|---|---|---|---|---|---|
| 1 | 0.0005032 | 2,432.6839108 | 10.8204873 | 4,054.4731847 | 202.7236592 | 2.4 × 10-16 | 0.0024 |
| 1,987.3411866 | 1 | 4,834,572.929895 | 21 504 | 8,057,621.5498223 | 402,881.0774932 | 4.76961884784 × 10-13 | 4.7696188 |
| 0.0004111 | 2.0684350293206 × 10-7 | 1 | 0.0044480 | 1.6666667 | 0.0833333 | 9.86564670138 × 10-20 | 9.86564670138 × 10-7 |
| 0.0924173 | 4.6502976190476 × 10-5 | 224.8220299 | 1 | 374.7033831 | 18.7351692 | 2.2180147171875 × 10-17 | 0.0002218 |
| 0.0002466 | 1.2410610175928 × 10-7 | 0.6000000 | 0.0026688 | 1 | 0.0500000 | 5.91938802083 × 10-20 | 5.91938802083 × 10-7 |
| 0.0049328 | 2.482122035173 × 10-6 | 12.0000000 | 0.0533756 | 20.0000000 | 1 | 1.18387760416 × 10-18 | 1.18387760416 × 10-5 |
| 4.1666666666667 × 1015 | 2 096 603 590 144 | 1.0136182961631 × 1019 | 4.5085363602457 × 1016 | 1.6893638269379 × 1019 | 8.4468191347325 × 1017 | 1 | 10 000 000 000 000 |
| 416.6666667 | 0.2096604 | 1,013,618.2961631 | 4,508.5363602 | 1,689,363.8269379 | 84,468.1913473 | 1.0 × 10-13 | 1 |
| 1 fluid barrels = 0.11562819898507 cubic meters |
| 2 fluid barrels = 0.23125639797015 cubic meters |
| 3 fluid barrels = 0.34688459695522 cubic meters |
| 4 fluid barrels = 0.4625127959403 cubic meters |
| 5 fluid barrels = 0.57814099492537 cubic meters |