There are two major classes of electoral quotas: “fixed” electoral quotas and “variable” electoral quotas.

1. The “fixed” electoral quota or uniform number: this is a number of votes predetermined by the legislature and identical for all constituencies. Use of this quota means that the number of seats in the assembly will not be determined until election night. The number of seats will, moreover, depend on the participation rate. Moreover, adoption of a “fixed” electoral quota tends to preclude the representation of a substantial number of votes, particularly those cast for small parties. Consequently, only the choice of a relatively low electoral quota, coupled with its application in large constituencies, is capable of curbing this tendency. This type of electoral quota has only been used in the Weimar Republic in Germany.

2. The “variable” electoral quota is determined on election night. There are various forms:

- The simple or Hare quota: this quota is obtained by dividing, in each constituency, the total number of votes cast (V) by the number of seats to be filled (S).

Hare quota = V/S

In practice, the Hare quota corresponds to the maximum number of votes which a candidate requires in order to be elected. The drawback with this system therefore is that it means that only a small number of seats can be allocated during the first distribution. It is, moreover, for this reason that other quotas have been formulated so as to allow the maximum possible number of seats to be allocated during the first stage of distribution.

- The Hagenbach-Bischoff quota: this quota is obtained by dividing, in each constituency, the total number of votes cast (V) by the number of seats (S) plus one.

Hagenbach-Bischoff quota = V/(S+1)

- The Droop quota: this quota is calculated in the same way as the Hagenbach-Bischoff quota, but one is added.

Droop Quota = V/(S+1) + 1

- The Imperiali quota: this quota is calculated in the same way as the Hagenbach-Bischoff quota but two is added to the divisor instead of one.

Imperiali Quota = V/(S+2)

- The double quota: this is, in a manner of speaking, a combination of the “fixed” electoral quota and the Hare quota. In the first instance, an initial electoral quota is fixed corresponding to the minimum number of votes needed to participate in the distribution of seats. A second electoral quota is then calculated which takes account only of the votes obtained by the lists which were successful in the first stage. 

The double quota must not be confused with a qualifying threshold for participating in the distribution of seats. First, the quota is expressed as a number of votes. Second, it is identical regardless of the constituency. The double quota is used chiefly in Latin America (Bolivia, Costa Rica, Ecuador).