At least several kilometers
These vessels were larger and more powerful than the later Acclamator-class assault ship, but they did not have trans-galactic hyperdrive capability, thus limiting them to localized conflicts. Unlike the standardized Republic Judicial Forces warships, these vessels were several kilometers long.
Centuries after the end of the New Sith Wars, rich, heavily industrialized Core sectors like Kuat built heavy warships to defend themselves, while the downsized Republic Navy and the poorer, rimward sectors operated a large amount of smaller vessels, like the Dreadnaught-class heavy cruiser. This situation lasted until the Clone Wars.
Behind the scenesEdit
Based on an official interview with Curtis Saxton at TheForce.net, Kuat sector warships were multi-kilometer long vessels, as were the warships employed by other rich and industrialized sectors in the Galactic Republic.