India has a population of approx 1.2B People.
About 20% are BPL and would therefore not use surf excel. Remaining population: o.8*1.2B = 0.96B people.
Assuming a family of 4 people that is 0.24B families.
Rural:Urban = 30:70 (0.072B:0.168B)
Assuming only about 10% of people use surf excel in ruler areas, due to the availability of other cheaper mediums that will be 16M Families.
Due to competition and availability of substitutes in urban areas, assuming surf excel has a market share of 40%, that will be about 28M families.
Total user base: 44M Families.
Everyday usage must be at least 10 grams, total usage = 440 Million gms of surf excel everyday.