In 1 pound / cubic meter [lb / m³] [metric] there is 500.0000305 parts per million [ppm].

grain / cubic meter [gr / m³] grain / gallon [gr / gal] [dry] grain / gallon [gr / gal] [fluid] grain / gallon [gr / gal] [imperial] grain / liter [gr / l] gram / cubic meter [g / m³] gram / liter [g / l] kilogram / liter [kg / l] parts per billion [ppb] parts per million [ppm] pound / cubic meter [lb / m³] [avoirdupois] pound / cubic meter [lb / m³] [metric] pound / cubic meter [lb / m³] [troy] pound / gallon [lb / gal] [avoirdupois, dry US] pound / gallon [lb / gal] [avoirdupois, fluid US] pound / gallon [lb / gal] [avoirdupois, imperial]

grain / cubic meter [gr / m³] grain / gallon [gr / gal] [dry] grain / gallon [gr / gal] [fluid] grain / gallon [gr / gal] [imperial] grain / liter [gr / l] gram / cubic meter [g / m³] gram / liter [g / l] kilogram / liter [kg / l] parts per billion [ppb] parts per million [ppm] pound / cubic meter [lb / m³] [avoirdupois] pound / cubic meter [lb / m³] [metric] pound / cubic meter [lb / m³] [troy] pound / gallon [lb / gal] [avoirdupois, dry US] pound / gallon [lb / gal] [avoirdupois, fluid US] pound / gallon [lb / gal] [avoirdupois, imperial]