A 4 mm² copper circuit on a 25 A curve C breaker can run 41 m at its full load. Voltage drop sets that length: at 41 m the drop reaches the 5 % limit of AS/NZS 3000:2018 Cl 3.6.2.
The case
The circuit is single‑phase at 230 V with a 2.5 mm² earth and a design current of 25 A at a power factor of 1. AS/NZS 3000:2018 Table B1 gives a fault loop length of 67 m for this cable and device.
What changes the answer
The length scales with the load. With 20 A of design current on the same breaker, the run can reach 51.25 m. The fault loop length does not change with the load. It depends on the cable and the breaker.
See also: What size cable for a 25 A circuit? and Voltage drop basics.