Tau

From PyroGuide

Typical 20,000 TAU celebration roll with head bomb and different sized firecrackers.

The term Tau pertains to firecracker rolls as a term of measurement.
Tau is a very old Chinese firework measuring system formula, it measures the total amount of charge in a roll of mixed firecrackers.
When observing most Tau rolls you see the mixture of different size firecrackers and head bombs. Figuring each charge is different because the larger firecrackers and head bombs contain more charge than an individual small firecracker. Therefore the total amount of charge changes, thus adding up to a certain Tau number.
For example, in a 100,000 Tau roll of red celebration firecrackers with head bombs and mixture of firecracker sizes there is somewhere around 16,000 crackers, however, the Tau measurement for the charge in that roll is equal to 100,000. In Tau rolls you don't count the total number of firecrackers. It is however many mixed firecrackers the Tau formula figured charge are on the roll equals the total amount Tau in said roll.

For examples are approximate Tau:

5000 Tau 1,388
10,000 Tau 2,462
20,000 Tau 4,526
100,000 Tau 16,298