Test tubes are available in a range of sizes, with widths varying from 10 to 20 mm and lengths ranging from 50 to 200 mm. The most commonly used size in laboratories is the standard 18 mm x 150 mm test tube.

      For more specific applications, there are also extra small (Durham) tubes, which measure either 5 mm x 35 mm or 4 mm x 40 mm. These tubes are ideal for detecting gases produced by microorganisms and are typically placed upside down to trap the gas.

     Smaller tubes, measuring 13 mm x 100 mm, can hold up to 9 ml of material and are useful for various experimental procedures. Medium-sized tubes, with dimensions of 16 mm x 150 mm, can accommodate approximately 22 ml of material.

     For larger volumes, there are large-sized tubes measuring 20 mm x 200 mm, capable of holding 28 ml of material. These tubes are suitable for experiments that require more space or volume.