The voivodeship had the area of 161.84 old-Polish sq. miles (= 8,912.87 km2 (3,441.28 sq mi))[1] (1 old-Polish mile: 7,5-8.5 km), with four powiaty (counties). When in 1396 the Wieluń Land returned to Poland, it became part of Sieradz Voivodeship, which increased the area to 212.25 old-Polish sq. miles (11,689.53 km2 (4,513.35 sq mi)),[1] and the number of counties to six. In the mid-16th century, the voivodeship (without the Wieluń Land) had 127 Roman Catholic parishes, 29 towns and 938 villages, while the Land of Wieluń had 67 parishes, 13 towns and 182 villages. Sieradz Voivodeship had five senators: the Voivode of Sieradz, the Castellan of Sieradz, and the Castellans of Rozprza, Spycimierz and Konary. Main starostas resided in Sieradz and Piotrków Trybunalski, there also were starostas at Radomsko, Szadek, Tuszyn, Klonowa, Warta and other locations. The sejmiks at Szadek elected four deputies to the Sejm, and two deputies to the Greater Poland Tribunal in Piotrków Trybunalski.
Wieluń Land, with the area of 50.41 old-Polish sq. miles,[1] had its own administrative system and a senator, who was the Castellan of Wieluń. It also had its own starostas, residing at Wieluń, Ostrzeszów, Grabów nad Prosną, and Bolesławiec, and elected two deputies to the Sejm, at the separate sejmiks in Wieluń. Furthermore, the Voivode of Sieradz named his deputy, who ruled the Wieluń Land.
^Atlas historyczny Polski. Województwo sieradzkie i województwo łęczyckie w drugiej połowie XVI wieku. Część I. Mapy, plany (in Polish). Warszawa: Instytut Historii Polskiej Akademii Nauk. 1998. pp. 3–4.
