CalcSD has a list of all available medically measured studies:
https://calcsd.info/study4.html
The global BP average is 5.5". Here's all the studies in that list grouped by location:
East
Hwnag: 4.61" (0.71) BPSFL
Choi: 4.61" (0.75) BPSFL
Son: 4.69" (0.51)
BPEL
Chen: 5.08" (0.51)
BPEL
Wu: 5.25" (0.44) BPSFL
Yoon: 5.28" (0.54) BPSFL
Wu & Yang: 5.32" (0.43)
BPEL
Park: 5.33" (0.66)
BPEL
Wu: 5.47" (0.44) BPSFL
Park: 5.54" (0.59)
BPEL
Nguyen: 5.75" (0.55) BPSFL
Overall ~5.2" (0.55)
Middle East
Chen: 4.92" (0.55) BPSFL
Hussein: 4.96" (0.75) BPSFL
Kamel: 5.08" (0.75) BPSFL
Awwad: 5.35" (0.67) BPSFL
Chen: 5.35" (0.67)
BPEL
Shalaby: 5.45" (0.53) BPSFL
Soylemez: 5.5" (0.62) BPSFL
Habous: 5.63" (0.79)
BPEL
Habous: 5.65" (0.73)
BPEL
Salama: 5.91" (0.71)
BPEL
Salama: 5.92" (0.59)
BPEL
Overall ~5.5" (0.69)
West
Acuna: 5.47" (0.67)
BPEL (but counted it as erect enough to get measured at 70% hardness)
Khan: 5.63" (0.66) BPSFL
Schneider: 5.7" (0.78)
BPEL
Gabrich: 5.7" (0.63) BPSFL
Stewart: 5.9" (0.67) BPSFL
Pereira: 5.96" (0.83) BPSFL
Wessels: 6.2" (1.03)
BPEL
Barboza: 6.32" (0.64) BPSFL
Vasconcelous: 6.54" (0.67) BPSFL
Bondil: 6.59" (0.9) BPSFL
Overall: ~6.1 (0.78)
3 SD above average - which is about 1 in 1000 - would be 6.9" BP in the East, 7.6" BP in the Middle East and 8.4" BP in the West
For NBP the global average is 5" and split up by location it looks like this:
East
Son: 3.78" (0.47) NBPSFL
Son: 3.86" (0.31) NBPSFL
Park: 4.24" (0.76) NBPSFL
Son: 4.25" (0.51)
NBPEL
Promodu: 4.28" (0.56) NBPSFL
Park: 4.68" (0.52)
NBPEL
Motofumi: 4.81" (0.68) NBPSFL
Park: 4.84" (0.52) NBPSFL
Promodu: 5.09" (0.64)
NBPEL
Wang & Li: 5.12" (0.51)
NBPEL
Yoon: 5.28" (0.54)
NBPEL
Overall ~4.5" (0.56)
Middle East
Mehraban: 4.56" (0.56) NBPSFL
Rad: 4.81" (0.96) NBPSFL
Habous: 4.93" (0.76)
NBPEL
Salama: 5.07" (0.57)
NBPEL
Hosseini: 5.12" (0.41) NBPSFL
Salama: 5.12" (0.67)
NBPEL
Aslan: 5.39" (0.63) NBPSFL
Ali & Ali: 5.39" (0.63)
NBPEL
Haliloglu: 5.59" (0.43) NBPSFL
West
Siminoski: 3.70" (0.55) NBPSFL (this is about the same size as the average flaccid penis, so they obviously did not stretch hard enough to get a reliable estimate of erect size)
Eisenberg: 4.70" (0.89) NBPSFL
Spyropoulos: 4.80" (0.67) NBPSFL
Wessels: 4.90" (1.07) NBPSFL
Ponchietti: 4.92" (0.98) NBPSFL
Eisenberg: 4.94" (0.80) NBPSFL
Wessels: 5.07" (1.15)
NBPEL
Savoie: 5.31" (1.02) NBPSFL
NBP studies are a bit problematic due to different levels of fat pad. Measured BP the Middle East is below the West, but NBP it's the other way around.