655.5 ppb to ppm

655.5 ppb = 0.655 ppm

ppbppm
640.5 ppb0.64
645.5 ppb0.645
650.5 ppb0.65
655.50.655
660.5 ppb0.66
665.5 ppb0.665
670.5 ppb0.67

655.5 ppb = 0.655 ppm

Formula

1 ppm = 1 mg/L (aqueous, density ≈ 1 kg/L) · 1 ppb = 0.001 mg/L · 1% = 10,000 ppm