The current loop area on a PCB which will cause problems with regard to legislative emission  requirements.

The E field strength limit at 3 m distance in Standards is 40 dBuVm^-1 or 100 uVm^-1.

Considering OATS measurement with +6 dB in-phase reflection from ground plane, the max loop area  that will not exceed specified level can be determined from:

A    =  380 E r
              f² I                         cm²

where:

E is radiation limit in microvolts per metre
r is distance to measurement in metres
f is frequency in MHz
I is current in milliamps

See page 301 of "Noise Reduction Techniques in Electronic Systems" by Henry Ott.