Why the constitution of India is the lengthiest constitution in the world ??

The Indian Constitution is the lengthiest and the most detailed of all the written constitutions of the world. 

 The American constitution originally consisted of only 7 Articles.

The Australian constitution consisted 128 Articles. 

The Canadian constitution 147 Articles. 

The Indian Constitution original consisted 395 articles divided into 22 parts and 8 schedules. 

             Since 1951, several Articles and parts have been added and several Articles have been omitted from the Constitution.

The extraordinary bulk of the Constitution is due to several reasons....are as follows -

    1) The framers of the Indian Constitution have gained experience from the working all the known Constitutions of the world. They were aware of the difficulties faced in the working of these Constitutions. This was the reason that they sought to incorporate good provisions of those Constitutions in order to avoid defects and loopholes that might come in future in the working of the Indian Constitution. Accordingly, they framed the chapter of the fundamental rights on the model of the American constitution, and adopted the parliamentary system of government from the United Kingdom , they took the idea of Directive Principles of State Policy from the constitution of Ireland,  and added elaborate provisions relating to emergency in the light of the Constitution of the German Reich and the Government of India Act 1935 .

2) The Indian Constitution lays down the structure not only of the central government but also the states. The American constitution leaves the state to draw up their own constitution.

3)  The vastness of the country and peculiar problems relating to the language have added to the bulk of the Constitution.

4) The constitution contains a long list of fundamental rights and also number of Directive Principles,  which confer no justifiable right upon the individual. Though these directives by their very nature could not be made legally enforceable yet the framers incorporated them in the Constitution with a view that it would serve as constant reminder to the Future government that they will have to implement them in order to achieve the ideals of the welfare state as envisaged in the Preamble of the Constitution. It was also felt that the smooth working of an infant democracy might be jeopardised unless the constitution mentioned in detail things which were left in other constitutions to ordinary legislation. This explains why we have in our constitution detailed to provisions about the organisations of the Judiciary, the services, the public service commissions,  Elections and many transitory  provisions.